How to do tracepath for the listening port linux

To Know the trace path of the port

Command:- 

#tracepath 10.73.107.61/5106

Output

[16:59:37] SPASERVERDBA:~ # tracepath 10.73.107.61/5106   
 1:  machine2.move.com (10.57.199.120)       0.086ms pmtu 1500
 1:  erpserver.move.com (10.57.199.221)      0.412ms 
 1:  dba-erpserver.move.com (10.57.199.2)    0.367ms 
 2:  venus.move.com (10.57.192.193)          0.580ms 
 3:  AC-move.com (10.57.192.34)              20.192ms 
 4:  movefirwall.move.com (10.73.97.127)     0.948ms 
 5:  moveswitch.move.com (10.73.97.176)      1.723ms 
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     Too many hops: pmtu 1500
     Resume: pmtu 1500 

How to Extend Volume Group in AIX

Steps to Follow:-

- create new LUN on storage
- run cfgmgr on target host to find new LUN as disk
- run smit and extend number of physical volumes for the logical volume
- run extendlv NAME_OF_LV SIZE_TO_EXTENT
+ here it was: "extendlv dbtest 20G" for new 20 gigabyte space
- run chfs -a size=+20480M to extend the filesystem
+ chfs requires 72 minutes to do the job, while there was no I/O on the filesystem

That all the dbtest will be extended 20GB.

பாரம்பரிய அரிசி வகைகளும் அதன் பயன்களும்

மாப்பிளை சம்பா :

     உடலை பலபடுத்தும் மாமருந்து .
திருமணதிற்கு தயாராகும் மணமகன்கள் தொடர்ச்சியாக 41 நாட்கள் இதன் நீராகாரத்தை உண்டு வந்தால் உடல் பலம் அதிகரிக்கும்.


கவுணி அரிசி :

     புது மாப்பிள்ளைகான விருந்துணவு அரிசி .
இதன் கஞ்சி குடித்தால் குதிங்கால் வலி நீங்கும் .


சிவப்பு கவுணி அரிசி :

     புது மண தம்பதியர் உண்ண வேண்டிய அரிசி . இது ஒரு பலகார அரிசி .
இட்லி,ஆப்பம், பணியாரம் செய்ய ஏதுவானது .

குழந்தைகளுக்கு நோயெதிர்ப்பு சக்தி தரும் .கருவில் குழந்தை நல்ல ஆரோக்கியத்துடன் உருவாகும் .


சேலம் சன்னா :

     கர்ப்பகாலத்தில் உண்ண வேண்டிய அரிசி .
குழந்தை பேரு நன்முறையில் நடக்கும் .
களைப்பில்லாமல் வேலை செய்ய உதவும் .
இது நாய் கடி விஷத்தை முறிக்கும் .


பூங்காற் அரிசி :

     மகப்பேறு காலங்களில் உண்ண வேண்டிய அரிசி .
தாய்பால் சுரக்கும் .


கட்ட சம்பா அரிசி :

    நோய் எதிர்ப்பு சக்தி தரும் .


சிங்கினி கார் அரிசி :

     எல்லா விதமான நோயாளிகளும் உண்ண வேண்டிய அரிசி .
உடல் நலம் பெற உதவும் .


இலுப்பைபூ சம்பா அரிசி :

     சர்க்கரை நோய் வராமல் தடுக்கும்.
மூட்டு வலி,பக்க வாதம் போன்ற நோய்க்கான மருந்து .
நரம்பு பிரச்சனையின் மருந்து .


காட்டுயானம் அரிசி :

     இந்த அரிசியில் காஞ்சி வைத்து கறிவேப்பில்லை போட்டு மூடி வைத்து , மறுநாள் காலையில் வெறும் வயிற்றில் குடிக்க வேண்டும் . இப்படி தொடர்ச்சியாக செய்தால் புற்றுநோயால் ஏற்படும் புண்கள் ஆறும் . இதுவே புற்று நோய்க்கு மருந்தாக இருக்க வேண்டும் என ஆய்வுகள் நடைபெற்று வருகிறது .


சூரகுருவை அரிசி :

     நோய் எதிர்ப்பு சக்தி தரும் .


பனங்காட்டு குடவாழை அரிசி :

     தொழிலாளர்களின் தோழன் இந்த அரிசி .
அந்த அளவிற்கு நோய் எதிர்ப்பும், உடல் வலிமையையும் தரும் .


கருடன் சம்பா :

     நோய் எதிர்ப்பு சக்தி தரும்.
சாப்பாடு மற்றும் பலகார அரிசி .


கருங்குறுவை அரிசி :

இதன் நெல் கரு நிறம். அரிசி செந்நிறம்
   
 இது ஒரு மாமருந்து.
இந்த அரிசியுடன் மூலிகை மருந்து சேர்த்தால் லேகியம் செய்ய முடியும் . அது யானைக்கால் நோய்க்கான மருந்து .

குஷ்டதிற்க்கும் , விஷகடிக்கும் மாமருந்து.

உடலை வலுவாக்கும் காயகல்ப சக்தி கொண்டது .

இந்த அரிசி ஒரு பங்கும், தண்ணீர் மூன்று பங்கும் சேர்த்து மண்பானையில் ஊரவைத்து ஆறுமாதம் கழித்து எடுத்தால் பால் போல் இருக்கும் . இதற்க்கு 'அன்ன காடி 'என்று பெயர் .இது காலராவிர்க்கான
மருந்து .

இது கிரியா ஊக்கியாக உள்ளது .


கார் அரிசி :
   
     சர்க்கரை நோய்க்கும், வாதம் சம்பந்தமான நோய்க்கும், கரப்பான் களுக்கும் மருந்தாகும்.


தங்க சம்பா :

     இந்த அரிசியை தொடர்ந்து உணவிலும் , பலகாரத்திலும் சேர்த்து வந்தால் முகம் பொலிவுடன் ஜொலிக்கும். நோய் எதிர்ப்பு திறனும் கொடுக்கும்.


தூயமல்லி அரிசி :

     மேல குறிப்பிட்ட எல்லா அரிசிகளும் சிவப்பரிசி . கட்ட சம்பா தவிர்த்து .
தூய மல்லி அரிசியானது இன்னும் மல்லிகை போல் பளபள வென இருக்ககூடியது .
மக்கள் எதிர்ப்பார்க்கும் எல்லா குணங்களும் கொண்ட ஒரு அரிசி .
தெவிட்டாத , நோய் எதிர்ப்பு சக்தி தரும் அரிசி .

இந்த பாரம்பரிய அரிசி எதுவும் உரமோ, பூச்சி கொல்லி மருந்தோ இல்லாமலேயே வளரக்கூடியது.

மேற்காணும் அரிசி வகைகள் தானாக வளரக்கூடியது . தானே எதிர்ப்பு திறனுடன் வளர்வதால் இந்த அரிசியை உன்னுபவர்களுக்கும் அதே எதிர்ப்பு சக்தியை கொடுக்கும் வல்லமை கொண்டது .

பாரம்பரிய அரிசி உண்போம் . உடலை வளர்ப்போம் . உயிரை காப்போம் .

( தொகுப்பாளர் ரா. பொன்னம்பலம் அவர்களின் 'நெல் அதிகாரம் 'என்ற புத்தகத்தில் இருந்து தொகுக்கப்பட்டது )


மேற்காணும் அரிசி வகைகள் அனைத்தும் , எல்லா இயற்கை உணவு அங்காடிகளில் கிடைக்கிறது . விலை சற்று அதிகம் . மருத்துவரிடம் கொடுப்பதில் பாதியை விவசாயிக்கும் கொடுக்கலாமே

Understanding Virtual Storage

vSphere 6.0:

Storage is one of the important features of configuring and managing your virtual environment. Storage options give the flexibility to set up your storage based on your cost, performance, and manageability requirements. Shared storage is useful for disaster recovery, high availability, and moving VMs from one host on another.

In this post, we’ll discuss some basic concepts of shared storage and storage protocols, datastores, file systems i-e VMFS, NFS, and vSAN, VVols.


Storage Overview

Datastores are the shared storage which are used to store VMs that are hosted on different ESXi hosts. ESXi hosts should be configured in a way that they can access shared storage.

Several storage technologies can be used with ESXi hosts to manage vSphere environment.

Direct Attached Storage: Storage disks which are directly connected to the ESXi host via a direct connection either internally or externally.

Fiber Channel (FC): is a high-speed transport protocol used for connecting SANs.

Fiber Channel over Ethernet (FCoE): FC traffic is encapsulated into FCoE frames. FCoE also reduces the network ports and cabling requirements.

iSCSI: is a SCSI transport protocol used to enable storage devices to transmit their data on TCP/IP network.

Network Attached Storage (NAS): in this storage technology, storage is shared at file system level over standard TCP/IP networks.


                         

Datastore:-

A shared storage amongst ESXi host is called datastore. A Datastore is a logical storage unit that can use a disk space on physical device or span several physical devices. Datastore is used to store VMs, templates, and ISO images.

vSphere supports following types of datastores:

VMFS
NFS
Virtual SAN (vSAN)
Virtual Volumes (VVol)
A VM is stored as a set of files in its own directory in a datastore. Datastores can also be used to store ISO images, VM templates.

VMFS5:-

Virtual Machine File System version 5 is a file system that store VMs files and allows concurrent access to shared storage. It enables following unique services:

Migration of VMs from one host to another without down time
A failed VM will be automatically restarted on a different host.
Clustering of VMs across several physical servers

VMFS datastore size can be increased dramatically upto 62TB when residing VMs are powered on and run. It uses 1 MB block size for storing large virtual disk files as well as 8 KB sub-block size for storing small files.

 

NFS:-

Network File System (NFS) is file sharing protocol that ESXi hosts use to communicate with a NAS device. NAS is a specialized storage device that connects to a network and can provide file access services to ESXi hosts.

NFS datastores are treated like VMFS datastores because they can be used to store VMs files, template, and ISO images. vMotion is also supported by NFS if VMs files are stores on NFS. NFS provides client in ESXi host communicates with the NFS server using NFS version 3.

vSAN:-

Virtual SAN is a hypervisor-converged, software-defined storage platform that is fully integrated with VMware vSphere. Virtual SAN aggregates locally attached disks of hosts that are members of a vSphere cluster (3 – 64 hosts per cluster), to create a distributed shared storage solution. Virtual SAN enables the rapid provisioning of storage within VMware vCenter as part of virtual machine creation and deployment operations.

Virtual SAN is the first policy-driven storage product designed for vSphere environments that simplifies and streamlines storage provisioning and management. Using VM-level storage policies, Virtual SAN automatically and dynamically matches requirements with underlying storage resources. With Virtual SAN, many manual storage tasks are automated – delivering a more efficient and cost-effective operational model.

Virtual SAN 6.0 provides two different configuration options, a hybrid configuration that leverages both flash-based devices and magnetic disks, and an all-flash configuration. The hybrid configuration uses server-based flash devices to provide a cache layer for optimal performance while using magnetic disks to provide capacity and persistent data storage. This delivers enterprise performance and a resilient storage platform. The all-flash configuration uses flash for both the caching layer and capacity layer.

VMwae recently released the latest version of vSAN 6.6 with new features and enhancements.



                 

VVols:-

VMware Virtual Volumes (VVols) are encapsulation of VMs and virtual disks and stored natively inside a storage system that is connected via SAN or Ethernet. VVols are created automatically when virtual machine management operations are performed.

VVols provide:

Reduced storage management overhead
Greater scalability
Lower cost of storage
Better response to data access
Better analytical requirements
You can follow detailed overview here written by Mohammed Raffic

Raw Device Mapping:-

Raw Device Mapping (RDM) is a file stored in a VMFS volume that acts as a proxy for a raw physical device. RDM enables you to store virtual machine data directly on a LUN. RDM is recommended when a VM must interact with a real disk on the SAN. This condition exists when you make disk array snapshots or have a large amount of data that you don’t want to move on to a virtual disk as part of a physical-to-virtual conversions.

Raw Device Mapping:-

         

All about Veritas NetBackup

Veritas Netbackup Basics

We’ll review NetBackup Enterprise Server and all the components involved in the backup process. This includes some licensing, installation and configuration concepts. I will only cover 3 TIER NetBackup Configurations.

Compatibility

NetBackup supports most popular operating systems such as Microsoft Windows, Unix, and Linux. For a complete list of support operating systems supported for the NetBackup Servers and NetBackup Clients refer to

http://www.symantec.com/docs/TECH76648.

As not all servers are physical these days there is also integration with Virtualization software platforms, VMware and Microsoft Hyper-V. Refer to

 http://www.symantec.com/docs/TECH127089 for details on virtualization.

In addition to all these operating systems NetBackup also supports the Applications and Databases residing on them. Custom Application and Database Agents allow the creation of consistent, online, and in certain cases granular, backups. For a complete list of support Applications and Databases refer to

http://www.symantec.com/docs/TECH126904

Then finally, backup is not possible without backup destinations or backup storage mediums. NetBackup supports a multitude of Storage Devices as backup targets. These include disk, tape, deduplication, and even cloud storage devices that are available from many vendors. For the full list of supported devices refer to http://www.symantec.com/docs/TECH76495.

The NetBackup Domain

NetBackup lets you backup, archive, and restore files, folders, and even complete systems that reside in your Datacenter. As mentioned in the previous section, NetBackup includes the Server, Client, Agent components:

The Master Server

The Master Server manages backups, archives, and restores operations. The configuration on the master server determine the following important criteria

The type backup (Files, Folders, Databases, Applications, Virtual guests)
The backup source (Client servers)
The transport method to use when backing up the data (LAN, SAN, Snapshots)
The backup targets or media (Storage Devices)
The retention (How long to retain the backup)
The configuration mentioned above is contained in the NetBackup Catalog. The Catalog consists of the following components.

Configuration files – Policies, schedules, any other flat files used by NetBackup
Relation Databases - Media and volume data used during backups, BMR info, and Authorization
NBDB.db
EMM_Data.db
EMM_Index.db
NBAZDB.db
BMRDB.db
Image Database - Information about what has been backed up and where the data resides.
An Enterprise Server License is required for the Master Server

The (Traditional) Media Server

The Media Server is responsible for receiving client data and placing it onto the backup storage media. Depending on the configuration that could be storage that is directly or indirectly available to the media server. (Indirectly implies that the data received is passed to storage server that would place it onto the storage media.)

A media server can perform backups of it and other clients where as a SAN media server can only perform backups of itself. These days the term SAN Media Server has been replaced by Enterprise Client although Enterprise Client is also a licensed feature, which includes more features than purely the ability to backup directly to a storage medium.

You can have the Media Server role or function enabled on your Master Server if you choose to. This is common in smaller configurations.

An Enterprise Server License is required for the Media Server

The FT Media Server

Performs the same role as the (Traditional) Media Server but receives the data from the Clients via the SAN instead of the LAN. Clients that send their data to an FT Media Server across the SAN are referred to as SAN Clients.

Only Solaris, and certain Linux Operating Systems are supported as FT Media Servers.

To enable the FT media server to receive data across the SAN it is required to change the fibre channel ports on the installed HBA’s to TARGET mode. Only certain HBA’s are supported for this configuration. Refer to the Operating System and Hardware compatibility guides in the previous section for more details.

A Media Server can act as both traditional and FT media server by receiving data via both the LAN and SAN.

An Enterprise Server License is required for the Media Server

The SAN Media Server / Enterprise Client

As explained earlier, a SAN media server can only perform backups of itself. This configuration is typically used for clients with larger data sets.

By converting the client to a SAN media server it could get access to the storage devices (tape / disk) directly and avoid sending its data across the LAN. The conversion would however require the installation of the Server software instead of the client software.

[I’ve listed the SAN Media Server / Enterprise Client under the Server Components because it runs Server software.]

An Enterprise Client License is required for the Media Server

The OpsCenter Server

The OpsCenter Server provides backup management, alerting, monitoring, and reporting capabilities for one or many NetBackup domains. According to the NetBackup 7.6. Licensing Guide

“There are two packages of OpsCenter: Standard and Analytics. The Standard OpsCenter functionality and reports are included with all NetBackup licensing. The customer is able to deploy OpsCenter within their environment as needed.


The base OpsCenter product and applicable support is available for customers who have a valid NetBackup license and corresponding support contract. No support will be provided customer without a valid NetBackup license.


OpsCenter Analytics Option builds on the OpsCenter standard features. OpsCenter Analytics enables advanced reporting capabilities such as a custom report builder and the ability to write custom SQL queries on the OpsCenter database. Furthermore, OpsCenter Analytics enables customer to access the entire history of their backup information. The base OpsCenter product limits customers to a 60-day window into their backup history.”

The (Standard) Client

The (Standard) Client is deployed on physical and virtual servers that are to be protected in the environment. In certain scenarios it is required to have the client software installed on a virtual guest even if it is being protected by a VMware of Hyper-V type policy, more on that later.

An Standard Client License is required for the Standard Client


The SAN Client

The SAN Client uses the same software as a (Standard) Client but is configured to send its data across the SAN to the FT Media Server. The features requires a valid Enterprise Client License, a configured FT media server, and some zoning configuration to work.

An Enterprise Client License is required for the SAN Client

The Storage Devices:-

NetBackup can store data in a multitude of storage devices. Below are the most common options.

Tape Devices:-

Standalone & Library Based Tape Drives can be used as backup destinations in NetBackup. Library based tape devices can be from either physical of virtual tape devices.
Shared Storage Option enables the sharing of above mentioned tape drives across NetBackup media servers on a storage area network (SAN).
NetBackup NDMP Option enables backup of NAS devices to local attached tape, to tape attached to another NDMP-compliant NAS device, or to an existing NetBackup media server.

Disk Devices

BasicDisk refers to locally-attached or network-attached disk devics. The disk storage is exposed as a file system to a NetBackup media server. NetBackup stores backup data in the specified directory. 

Advanced Disk Storage are primarily the same as BasicDisk devices but with added features such as sharing, load balancing, and the use of Storage Lifecycle policies.

OpenStorage (OST) Devices

Storage vendors (DataDomain, Quantum, etc) participate in the Symantec OpenStorage Partner Program. By using the OST API NetBackup can initiate or manage operations where the OST devices create secondary copies via duplication, replication, or export/dump to tape.

NetBackup Appliances

NetBackup 50xx series appliances offer a solution similar to the OST storage servers mentioned above in that they provide a deduplication storage server and disk storage
NetBackup 52xx series appliances are all-in-one / purpose built deduplication appliances and contain a media server in addition to the deduplication storage server and disk storage.

Data Paths

As seen in the section about the NetBackup Domain, there are many different server and client configuration option which influence how data is transferred from source to destination. In the explanation below we focus more on the path from the source up to the media server. We'll not focus on the subsequent transfer to the storage device as that would relate more to the type of device used.

Standard Client and (Traditional) Media Server

Client >>> LAN >>> Media Server >>> Storage Device/Storage Server

SAN Client and FT Media Server

Client >>> SAN >>> FT Media Server >>> Storage Device/Storage Server

Enterprise Client (Client and Media Server process run on same server)

[Client [>>> Media Server ] ] >>> Storage Device/Storage Server

Troubleshoot "blue screen" or Stop error problems

Try the following methods to troubleshoot Stop error messages:

Review the "bugcheck" code that you find in the event logs. Search for the specific Stop error codes to see whether there are any known issues, resolutions, or workarounds for the problem.


Does the error message indicate any specific driver in regards to the problem? If so, update the driver in question.


Take a detailed look at the event logs on the system. Are you seeing any indication of a service starting or stopping before the crash occurred? Is this service behavior consistent across all instances of the crash? 

If so, you can contact the software vendor for the service to receive updated versions of the software to check whether this resolves the problem.

Try to identify whether you have made any software or hardware change or modification. 

You may want to consider the option to roll back the changes or use the change management to follow standard practices to revert to the last working state. 

Additionally, you may want to contact the software or hardware vendor for more help.

As a best practice, we recommend that you make sure that the BIOS is updated and that hardware and memory tests are performed.

Are you observing behavior that is related to the crashes, and do you believe that you can trigger the crash? Did you reach out to the software vendor for any updated version of the software or drivers that may be triggering the crash?

Make sure that you save the memory dump files for review. These dump files have been validated by using DumpChk and are not corrupted or invalid. You can verify the memory dump by using the Microsoft DumpChk (Crash Dump File Checker) tool. 

For more information, go to the following Knowledge Base article:

315271 How to use Dumpchk.exe to check a Memory Dump file

Make sure that you install the latest Windows updates, cumulative updates, and rollup updates.

Upload the memory dumps that you have verified by using the DmpChk memory dump collector.


This diagnostic tool collects the last five machine mini-dump files from the past 30 days. 

It collects machine memory dump files from a computer and checks for known solutions. 

For more information about Machine Memory Dump Collector, go to the following Knowledge Base article:


2027760 [SDP 3][06bb55c8-3207-406e-a3fc-f538867a399b] Machine Memory Dump Collector - Windows

Oracle RAC and ASM Interview Questions & Answer Interview Questions & Answer

RAC,ASM,VOTING DISK 

Q What is SCAN?


Single Client Access Name (SCAN) is s a new Oracle Real Application Clusters (RAC) 11g Release 2 feature that provides a single name for clients to access an Oracle Database running in a cluster. The benefit is clients using SCAN do not need to change if you add or remove nodes in the cluster.


 Q what is dynamic remastering ? When will the dynamic remastering happens?


dynamic remastering is ability to move the ownership of resource from one instance to another instance in RAC. dynamic resource remastering is used to implement for resource affinity for increased performance. resource affinity optimized the system in situation where update transactions are being executed in one instance. when activity shift to another instance the resource affinity correspondingly move to another instance. If activity is not localized then resource ownership is hashed to the instance.

In 10g dynamic remastering happens in file+object level.the process of remastering is very stringent. For one instance should touch more than 50 times than the other instance in particular period(say 10 mints). this touch ratio and time can be tuned by gc_affinity_limit and _gc_affinity_time parameter.



 Q why we required to maintain odd number of voting disks?


Odd number of disk are to avoid split brain, When Nodes in cluster can't talk to each other they run to lock the Voting disk and whoever lock the more disk will survive, if disk number are even there are chances that node might lock 50% of disk (2 out of 4) then how to decide which node to evict. 
whereas when number is odd, one will be higher than other and each for cluster to evict the node with less number



 Q How you check the health of Your RAC Database?

 'crsctl' command from root or oracle user can be used to check the clusterware health But for starting or stopping we have to use root user or any privilege user.

[oracle@TEST_NODE1 ~]$ crsctl check crs
CSS appears healthy
CRS appears healthy
EVM appears healthy



 Q How you check the services in RAC Node?

 We can check the service or start the services with 'srvctl' command.load balanced/TAF service named RAC online.

[oracle@TEST_NODE1 ~]$ srvctl start service -d orcl -s RAC
[oracle@TEST_NODE1 ~]$ crsstat



 Q If there is some issue with virtual IP how will you troubleshoot it?How will you change virtual ip?

 To change the VIP (virtual IP) on a RAC node, use the command
[oracle@testnode oracle]$ srvctl modify nodeapps -A new_address



 Q How you will backup your RAC Database?

 Backup strategy of RAC Database:
An RAC Database consists of
1)OCR
2)Voting disk &
3)Database files, controlfiles, redolog files & Archive log files


 Q Do you have any idea of load balancing in application?How load balancing is done?

http://practicalappsdba.wordpress.com/category/for-master-apps-dbas/



 Q What is RAC?


RAC stands for Real Application cluster. It is a clustering solution from Oracle Corporation that ensures high availability of databases by providing instance failover, media failover features.



 Q What is RAC and how is it different from non RAC databases?


RAC stands for Real Application Cluster, you have n number of instances running in their own separate nodes and based on the shared storage. Cluster is the key component and is a collection of servers operations as one unit. RAC is the best solution for high performance and high availably. Non RAC databases has single point of failure in case of hardware failure or server crash.



 Q Give the usage of srvctl ?

srvctl start instance -d db_name -i "inst_name_list" [-o start_options]

srvctl stop instance -d name -i "inst_name_list" [-o stop_options]

srvctl stop instance -d orcl -i "orcl3,orcl4" -o immediate

srvctl start database -d name [-o start_options]

srvctl stop database -d name [-o stop_options]

srvctl start database -d orcl -o mount



 Q Mention the Oracle RAC software components ?

Oracle RAC is composed of two or more database instances. They are composed of Memory structures and background processes same as the single instance database.Oracle RAC instances use two processes GES(Global Enqueue Service), GCS(Global Cache Service) that enable cache fusion.Oracle RAC instances are composed of following background processes:

ACMS—Atomic Controlfile to Memory Service (ACMS)
GTX0-j—Global Transaction Process
LMON—Global Enqueue Service Monitor
LMD—Global Enqueue Service Daemon
LMS—Global Cache Service Process
LCK0—Instance Enqueue Process
RMSn—Oracle RAC Management Processes (RMSn)
RSMN—Remote Slave Monitor



 Q What is GRD?



GRD stands for Global Resource Directory. The GES and GCS maintains records of the statuses of each datafile and each cahed block using global resource directory.This process is referred to as cache fusion and helps in data integrity.



 Q What are the different network components are in 10g RAC?


public, private, and vip components
Private interfaces is for intra node communication. VIP is all about availability of application. When a node fails then the VIP component fail over to some other node, this is the reason that all applications should based on vip components means tns entries should have vip entry in the host list



 Q Give Details on ACMS:


ACMS stands for Atomic Controlfile Memory Service.In an Oracle RAC environment ACMS is an agent that ensures a distributed SGA memory update(ie)SGA updates are globally committed on success or globally aborted in event of a failure.



 Q What are the major RAC wait events?

In a RAC environment the buffer cache is global across all instances in the cluster and hence the processing differs.The most common wait events related to this are gc cr request and gc buffer busy

GC CR request :the time it takes to retrieve the data from the remote cache

Reason: RAC Traffic Using Slow Connection or Inefficient queries (poorly tuned queries will increase the amount of data blocks requested by an Oracle session. The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect.)

GC BUFFER BUSY: It is the time the remote instance locally spends accessing the requested data block.


 Q Give details on GTX0-j 

The process provides transparent support for XA global transactions in a RAC environment.The database autotunes the number of these processes based on the workload of XA global transactions.


 Q Give details on LMON

This process monitors global enques and resources across the cluster and performs global enqueue recovery operations.This is called as Global Enqueue Service Monitor.


 Q Give details on LMD

This process is called as global enqueue service daemon. This process manages incoming remote resource requests within each instance.


 Q Give details on LMS

This process is called as Global Cache service process.This process maintains statuses of datafiles and each cahed block by recording information in a Global Resource Dectory(GRD).This process also controls the flow of messages to remote instances and manages global data block access and transmits block images between the buffer caches of different instances.This processing is a part of cache fusion feature.


 Q Give details on LCK0

This process is called as Instance enqueue process.This process manages non-cache fusion resource requests such as libry and row cache requests.


 Q Give details on RMSn

This process is called as Oracle RAC management process.These pocesses perform managability tasks for Oracle RAC.Tasks include creation of resources related Oracle RAC when new instances are added to the cluster.



Q How to export and import crs resources while migrating Oracle RAC to new server?



Below script generate svrctl add script for database, instance, service and 11G listeners from OCR from current RAC.
Save the result of the script and run it at new RAC.

for DBNAME in $(srvctl config database)
do

# Generate DB resource

srvctl config database -d $DBNAME -a | awk -v dbname="$DBNAME" \
'BEGIN { FS=":" }
$1~/Oracle home/ || $1~/ORACLE_HOME/ {dbhome = "-o" $2}
$1~/Spfile/ || $1~/SPFILE/ {spfile = "-p" $2}
$1~/Disk Groups/ {dg = "-a" $2}
END { if (avail == "-a ") {avail = ""}; printf "%s %s %s %s %s\n", "srvctl add database -d ", dbname, dbhome, spfile, dg }'

# Generate Instance resource

srvctl status database -d $DBNAME | awk -v dbname="$DBNAME" \
'$4~/running/ { printf "%s %s %s %s %s %s\n", "srvctl add instance -d ",dbname, " -i ", $2 ," -n ", $7 }
$5~/running/ { printf "%s %s %s %s %s %s \n", "srvctl add instance -d ",dbname, " -i ", $2 ," -n ", $8 }'

# Modify instance for 10G - ASM dependency

if [ $(echo $ORACLE_HOME | grep "1020" | wc -l ) -eq 1 ]
then
srvctl status database -d $DBNAME | awk -v dbname="$DBNAME" \
'$2~/1$/ { printf "%s %s %s %s %s \n", "srvctl modify instance -d ",dbname, " -i ", $2 ," -s +ASM1" }
$2~/2$/ { printf "%s %s %s %s %s \n", "srvctl modify instance -d ",dbname, " -i ", $2 ," -s +ASM2" }
$2~/3$/ { printf "%s %s %s %s %s \n", "srvctl modify instance -d ",dbname, " -i ", $2 ," -s +ASM3" }
$2~/4$/ { printf "%s %s %s %s %s \n", "srvctl modify instance -d ",dbname, " -i ", $2 ," -s +ASM4" }'
fi

echo "srvctl start database -d $DBNAME"

# Generate Service resource

snamelist=$(srvctl status service -d $DBNAME | awk '{print $2}')

for sname in $snamelist
do
srvctl config service -d $DBNAME -s $sname| awk -v dbname="$DBNAME" -v sname=$sname \
'BEGIN { FS=":"}
$1~/Preferred instances/ {pref = "-r" $2}
$1~/PREF/ {pref = "-r" $2; sub(/AVAIL/, "", pref) }
$1~/Available instances/ {avail = "-a" $2}
$2~/AVAIL/ {avail = "-a" $3}
$1~/Failover type/ {ft = "-e" $2}
$1~/Failover method/ {fm = "-m" $2}
$1~/Runtime Load Balancing Goal/ {g = "-B" $2}
END { if (avail == "-a ") {avail = ""}; printf "%s %s %s %s %s %s %s %s %s %s\n", "srvctl add service -d ",dbname, "-s ", sname, pref, avail ,ft, fm,g, "-P BASIC"}'
echo "srvctl start service -d $DBNAME -s $sname"
done
done

# Listener at 11G Home. 10G listener can't ba added with srvctl.


srvctl config listener | awk \
'BEGIN { FS=":"; state = 0; }
$1~/Name/ {lname = "-l" $2; state=1};
$1~/Home/ && state == 1 {ohome = "-o" $2; state=2;}
$1~/End points/ && state == 2 {lport = "-p " $3; state=3;}
state == 3 {if (ohome != "-o ") {printf "%s %s %s %s\n", "srvctl add listener ", lname, ohome, lport;} state=0;}'



 Q Give details on RSMN?


This process is called as Remote Slave Monitor.This process manages background slave process creation andd communication on remote instances. This is a background slave process.This process performs tasks on behalf of a co-ordinating process running in another instance.



 Q What components in RAC must reside in shared storage?


All datafiles, controlfiles, SPFIles, redo log files must reside on cluster-aware shred storage.



 Q What is the significance of using cluster-aware shared storage in an Oracle RAC environment?


All instances of an Oracle RAC can access all the datafiles,control files, SPFILE's, redolog files when these files are hosted out of cluster-aware shared storage which are group of shared disks.



 Q Give few examples for solutions that support cluster storage?


ASM(automatic storage management),raw disk devices,network file system(NFS), OCFS2 and OCFS(Oracle Cluster Fie systems).


 Q What is an interconnect network?

An interconnect network is a private network that connects all of the servers in a cluster. The interconnect network uses a switch/multiple switches that only the nodes in the cluster can access.


 Q How can we configure the cluster interconnect?


Configure User Datagram Protocol(UDP) on Gigabit ethernet for cluster interconnect.On unix and linux systems we use UDP and RDS(Reliable data socket) protocols to be used by Oracle Clusterware.Windows clusters use the TCP protocol.



 Q Can we use crossover cables with Oracle Clusterware interconnects?

No, crossover cables are not supported with Oracle Clusterware intercnects.



 Q What is the use of cluster interconnect?

Cluster interconnect is used by the Cache fusion for inter instance communication.



 Q How do users connect to database in an Oracle RAC environment?


Users can access a RAC database using a client/server configuration or through one or more middle tiers ,with or without connection pooling.Users can use oracle services feature to connect to database.



 Q What is the use of a service in Oracle RAC environment?

Applications should use the services feature to connect to the Oracle database.Services enable us to define rules and characteristics to control how users and applications connect to database instances.



 Q What are the characteristics controlled by Oracle services feature?

The charateristics include a unique name, workload balancing and failover options,and high availability characteristics.



 Q What enables the load balancing of applications in RAC?


Oracle Net Services enable the load balancing of application connections across all of the instances in an Oracle RAC database.



 Q What is a virtual IP address or VIP?

A virtl IP address or VIP is an alternate IP address that the client connectins use instead of the standard public IP address. To configureVIP address, we need to reserve a spare IP address for each node, and the IP addresses must use the same subnet as the public network.



 Q What is the use of VIP?

If a node fails, then the node's VIP address fails over to another node on which the VIP address can accept TCP connections but it cannot accept Oracle connections.



 Q Give situations under which VIP address failover happens?


VIP addresses failover happens when the node on which the VIP address runs fails, all interfaces for the VIP address fails, all interfaces for the VIP address are disconnected from the network.



 Q What is the significance of VIP address failover?


When a VIP address failover happens, Clients that attempt to connect to the VIP address receive a rapid connection refused error .They don't have to wait for TCP connection timeout messages.



 Q What are the administrative tools used for Oracle RAC environments?


Oracle RAC cluster can be administered as a single image using OEM(Enterprise Manager),SQL*PLUS,Servercontrol(SRVCTL),clusterverificationutility(cvu),DBCA,NETCA



 Q How do we verify that RAC instances are running?


Issue the following query from any one node connecting through SQL*PLUS.
$connect sys/sys as sysdba
SQL>select * from V$ACTIVE_INSTANCES;
The query gives the instance number under INST_NUMBER column,host_:instancename under INST_NAME column.



 Q What is FAN?

Fast application Notification as it abbreviates to FAN relates to the events related to instances,services and nodes.This is a notification mechanism that Oracle RAc uses to notify other processes about the configuration and service level information that includes service status changes such as,UP or DOWN events.Applications can respond to FAN events and take immediate action.



 Q Where can we apply FAN UP and DOWN events?



FAN UP and FAN DOWN events can be applied to instances,services and nodes.
State the use of FAN events in case of a cluster configuration change?
During times of cluster configuration changes,Oracle RAC high availability framework publishes a FAN event immediately when a state change occurs in the cluster.So applications can receive FAN events and react immediately.This prevents applications from polling database and detecting a problem after such a state change.



 Q Why should we have seperate homes for ASm instance?



It is a good practice to have ASM home seperate from the database hom(ORACLE_HOME).This helps in upgrading and patching ASM and the Oracle database software independent of each other.Also,we can deinstall the Oracle database software independent of the ASM instance.



Q What is the advantage of using ASM?

Having ASM is the Oracle recommended storage option for RAC databases as the ASM maximizes performance by managing the storage configuration across the disks.ASM does this by distributing the database file across all of the available storage within our cluster database environment.



 Q What is rolling upgrade?

It is a new ASM feature from Database 11g.ASM instances in Oracle database 11g release(from 11.1) can be upgraded or patched using rolling upgrade feature. This enables us to patch or upgrade ASM nodes in a clustered environment without affecting database availability.During a rolling upgrade we can maintain a functional cluster while one or more of the nodes in the cluster are running in different software versions.



 Q Can rolling upgrade be used to upgrade from 10g to 11g database?



No,it can be used only for Oracle database 11g releases(from 11.1).



 Q State the initialization parameters that must have same value for every instance in an Oracle RAC database?


Some initialization parameters are critical at the database creation time and must have same values.Their value must be specified in SPFILE or PFILE for every instance.The list of parameters that must be identical on every instance are given below:
ACTIVE_INSTANCE_COUNT
ARCHIVE_LAG_TARGET
COMPATIBLE
CLUSTER_DATABASE
CLUSTER_DATABASE_INSTANCE
CONTROL_FILES
DB_BLOCK_SIZE
DB_DOMAIN
DB_FILES
DB_NAME
DB_RECOVERY_FILE_DEST
DB_RECOVERY_FILE_DEST_SIZE
DB_UNIQUE_NAME
INSTANCE_TYPE (RDBMS or ASM)
PARALLEL_MAX_SERVERS
REMOTE_LOGIN_passWORD_FILE
UNDO_MANAGEMENT



 Q What is ORA-00603: ORACLE server session terminated by fatal error or ORA-29702: error occurred in Cluster Group Service operation?



RAC node name was listed in the loopback address...



 Q Can the DML_LOCKS and RESULT_CACHE_MAX_SIZE be identical on all instances?



These parameters can be identical on all instances only if these parameter values are set to zero.
What two parameters must be set at the time of starting up an ASM instance in a RAC environment?The parameters CLUSTER_DATABASE and INSTANCE_TYPE must be set.



 Q Mention the components of Oracle clusterware?


Oracle clusterware is made up of components like voting disk and Oracle Cluster Registry(OCR).


 Q What is a CRS resource?

Oracle clusterware is used to manage high-availability operations in a cluster.Anything that Oracle Clusterware manages is known as a CRS resource.Some examples of CRS resources are database,an instance,a service,a listener,a VIP address,an application process etc.


 Q What is the use of OCR?



Oracle clusterware manages CRS resources based on the configuration information of CRS resources stored in OCR(Oracle Cluster Registry).



 Q How does a Oracle Clusterware manage CRS resources?


Oracle clusterware manages CRS resources based on the configuration information of CRS resources stored in OCR(Oracle Cluster Registry).


 Q Name some Oracle clusterware tools and their uses?


OIFCFG - allocating and deallocating network interfaces
OCRCONFIG - Command-line tool for managing Oracle Cluster Registry
OCRDUMP - Identify the interconnect being used
CVU - Cluster verification utility to get status of CRS resources



 Q What are the modes of deleting instances from ORacle Real Application cluster Databases?



We can delete instances using silent mode or interactive mode using DBCA(Database Configuration Assistant).


 Q How do we remove ASM from a Oracle RAC environment?



We need to stop and delete the instance in the node first in interactive or silent mode.After that asm can be removed using srvctl tool as follows:
srvctl stop asm -n node_name
srvctl remove asm -n node_name
We can verify if ASM has been removed by issuing the following command:
srvctl config asm -n node_name


 Q How do we verify that an instance has been removed from OCR after deleting an instance?

Issue the following srvctl command:
srvctl config database -d database_name
cd CRS_HOME/bin
./crs_stat



 Q How do we verify an existing current backup of OCR?



We can verify the current backup of OCR using the following command : ocrconfig -showbackup
What are the performance views in an Oracle RAC environment?
We have v$ views that are instance specific. In addition we have GV$ views called as global views that has an INST_ID column of numeric data type.GV$ views obtain information from individual V$ views.
What are the types of connection load-balancing?
There are two types of connection load-balancing:server-side load balancing and client-side load balancing.



 Q What is the difference between server-side and client-side connection load balancing?


Client-side balancing happens at client side where load balancing is done using listener.In case of server-side load balancing listener uses a load-balancing advisory to redirect connections to the instance providing best service.



 Q What are the three greatest benefits that RAC provides??


The three main benefits are availability, scalability, and the ability to use low cost commodity hardware. RAC allows an application to scale vertically, by adding CPU, disk and memory resources to an individual server. But RAC also provides horizontal scalability, which is achieved by adding new nodes into the cluster. RAC also allows an organization to bring these resources online as they are needed. This can save a small or midsize organization a lot of money in the early stages of a project.

In a RAC environment, if a node in the cluster fails, the application continues to run on the surviving nodes contained in the cluster. If your application is configured correctly, most users won't even know that the node they were running on became unavailable.



 Q What are the major RAC wait events?



In a RAC environment the buffer cache is global across all instances in the cluster and hence the processing differs.The most common wait events related to this are gc cr request and gc buffer busy

GC CR request: the time it takes to retrieve the data from the remote cache

Reason: RAC Traffic Using Slow Connection or Inefficient queries (poorly tuned queries will increase the amount of data blocks
requested by an Oracle session. The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect.)

GC BUFFER BUSY: It is the time the remote instance locally spends accessing the requested data block.



 Q What are the different network components in Oracle 10g RAC?

We have public, private, and VIP components. Private interfaces is for intra node communication. VIP is all about availability of application. When a node fails then the VIP component will fail over to some other node, this is the reason that all applications should be based on VIP components.  This means that tns entries should have VIP entry in the host list.


 Q Tune the following RAC DATABASE (DBNAME=PROD) which is 3 node RAC?


PROD1             PROD2                     PROD3
CPU 8               CPU 15                    CPU 8
32 GB RAM       12 GB RAM             16 GB RAM


What are you looking for here? What tuning information do you expect?


It is a 3 node cluster with different hardware configuration running RAC.
I would put 20% of the memory for Oracle in each node. So that would mean that the SGA is different in each of the nodes.
Also since the CPU's are different PROD2 can have more number of max number of processes as compared to the rest of them.
But as I said this is just configuration, this is not tuning. Question is not clear.


 Q Write a sample script for RMAN for the recovery if all the instance are down.(First explain the procedure how you will restore)?


Bring all nodes down.
Start one Node
Restore all datafiles and archive logs.
Recover 1 Node.
Open the database.
bring other nodes up.
Confirm that all nodes are operational.

 Clients are performing some operation and suddenly one of the datafile is experiencing problem what do you do? The cluster is a two node one.

Bring the datafile offline recover the datafile.


How can you connect to a specific node in a RAC environment?


tnsnames.ora ensure that you have INSTANCE_NAME specified in it.


 Q How to move OCR and Voting disk to new storage device?


Moving OCR
==========


You must be logged in as the root user, because root owns the OCR files. Also an ocrmirror must be in place before trying to replace the OCR device.

Make sure there is a recent backup of the OCR file before making any changes:

ocrconfig –showbackup

If there is not a recent backup copy of the OCR file, an export can be taken for the current OCR file. Use the following command to generate an export of the online OCR file:

In 10.2

# ocrconfig –export -s online

In 11g

# ocrconfig -manualbackup

The new OCR disk must be owned by root, must be in the oinstall group, and must have permissions set to 640. Provide at least 100 MB disk space for the OCR.

On one node as root run:

# ocrconfig -replace ocr 
# ocrconfig -replace ocrmirror 

Now run ocrcheck to verify if the OCR is pointing to the new file


Moving Voting Disk
==================


Note: crsctl votedisk commands must be run as root

Shutdown the Oracle Clusterware (crsctl stop crs as root) on all nodes before making any modification to the voting disk. Determine the current voting disk location using:

crsctl query css votedisk

Take a backup of all voting disk:

dd if=voting_disk_name of=backup_file_name

To move a Voting Disk, provide the full path including file name:

crsctl delete css votedisk –force
crsctl add css votedisk –force

After modifying the voting disk, start the Oracle Clusterware stack on all nodes

# crsctl start crs

Verify the voting disk location using

crsctl query css votedisk



 Q What is runfixup.sh script in Oracle Clusterware 11g release 2 installation?


With Oracle Clusterware 11g release 2, Oracle Universal Installer (OUI) detects when the minimum requirements for an installation are not met, and creates shell scripts, called fixup scripts, to finish incomplete system configuration steps. If OUI detects an incomplete task, then it generates fixup scripts (runfixup.sh). You can run the fixup script after you click the Fix and Check Again Button.

The Fixup script does the following:

■ If necessary sets kernel parameters to values required for successful installation,

including:

– Shared memory parameters.

– Open file descriptor and UDP send/receive parameters.

■ Sets permissions on the Oracle Inventory (central inventory) directory.

■ Reconfigures primary and secondary group memberships for the installation

owner, if necessary, for the Oracle Inventory directory and the operating system

privileges groups.

■ Sets shell limits if necessary to required values.



 Q When exactly during the installation process are clusterware components created?


After fulfilling the pre-installation requirements, the basic installation steps to follow are:

1. Invoke the Oracle Universal Installer (OUI)

2. Enter the different information for some components like:
- name of the cluster
- public and private node names
- location for OCR and Voting Disks
- network interfaces used for RAC instances
-etc.

3. After the Summary screen, OUI will start copying under the $CRS_HOME (this is the $ORACLE_HOME for Oracle Clusterware) in the local node the libraries and executables.
- here we will have the daemons and scripts init.* created and configured properly.

Oracle Clusterware is formed of several daemons, each one of which have a special function inside the stack. Daemons are executed via the init.* scripts (init.cssd, init.crsd and init.evmd).

- note that for CRS only some client libraries are recreated, but not all the executables (as for the RDBMS).

4. Later the software is propagated to the rest of the nodes in the cluster and the oraInventory is updated.

5. The installer will ask to execute root.sh on each node. Until this step the software for Oracle Clusterware is inside the $CRS_HOME.

Running root.sh will create several components outside the $CRS_HOME:

- OCR and VD will be formated.

- control files (or SCLS_SRC files ) will be created with the correct contents to start Oracle Clusterware.

These files are used to control some aspects of Oracle Clusterware like:
- enable/disable processes from the CSSD family (Eg. oprocd, oslsvmon)
- stop the daemons (ocssd.bin, crsd.bin, etc).
- prevent Oracle Clusterware from being started when the machine boots.
- etc.

- /etc/inittab will be updated and the init process is notified.

In order to start the Oracle Clusterware daemons, the init.* scripts first need to be run. These scripts are executed by the daemon init. To accomplish this some entries must be created in the file /etc/inittab.

- the different processes init.* (init.cssd, init.crsd, etc) will start the daemons (ocssd.bin, crsd.bin, etc). When all the daemons are running then we can say that the installation was successful

- On 10.2 and later, running root.sh on the last node in the cluster also will create the nodeapps (VIP, GSD and ONS). On 10.1, VIPCA is executed as part of the RAC installation.

6. After running root.sh on each node, we need to continue with the OUI session. After pressing the 'OK' button OUI will include the information for the public and cluster_interconnect interfaces. Also CVU (Cluster Verification Utility) will be executed.


 Q What are Oracle Clusterware processes for 10g on Unix and Linux?


Cluster Synchronization Services (ocssd) — Manages cluster node membership and runs as the oracle user; failure of this process results in cluster restart.

Cluster Ready Services (crsd) — The crs process manages cluster resources (which could be a database, an instance, a service, a Listener, a virtual IP (VIP) address, an application process, and so on) based on the resource's configuration information that is stored in the OCR. This includes start, stop, monitor and failover operations. This process runs as the root user

Event manager daemon (evmd) —A background process that publishes events that crs creates.

Process Monitor Daemon (OPROCD) —This process monitor the cluster and provide I/O fencing. OPROCD performs its check, stops running, and if the wake up is beyond the expected time, then OPROCD resets the processor and reboots the node. An OPROCD failure results in Oracle Clusterware restarting the node. OPROCD uses the hangcheck timer on Linux platforms.

RACG (racgmain, racgimon) —Extends clusterware to support Oracle-specific requirements and complex resources. Runs server callout scripts when FAN events occur.

 Q What are Oracle database background processes specific to RAC


•LMS—Global Cache Service Process

•LMD—Global Enqueue Service Daemon

•LMON—Global Enqueue Service Monitor

•LCK0—Instance Enqueue Process

To ensure that each Oracle RAC database instance obtains the block that it needs to satisfy a query or transaction, Oracle RAC instances use two processes, the Global Cache Service (GCS) and the Global Enqueue Service (GES). The GCS and GES maintain records of the statuses of each data file and each cached block using a Global Resource Directory (GRD). The GRD contents are distributed across all of the active instances.



Q What are Oracle Clusterware Components?



Voting Disk — Oracle RAC uses the voting disk to manage cluster membership by way of a health check and arbitrates cluster ownership among the instances in case of network failures. The voting disk must reside on shared disk.

Oracle Cluster Registry (OCR) — Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR must reside on shared disk that is accessible by all of the nodes in your cluster



 Q How do you troubleshoot node reboot ?


Please check metalink ...

Note 265769.1 Troubleshooting CRS Reboots
Note.559365.1 Using Diagwait as a diagnostic to get more information for diagnosing Oracle Clusterware Node evictions.

 Q How do you backup the OCR

There is an automatic backup mechanism for OCR. The default location is : $ORA_CRS_HOME\cdata\"clustername"\

To display backups :
#ocrconfig -showbackup
To restore a backup :
#ocrconfig -restore

With Oracle RAC 10g Release 2 or later, you can also use the export command:
#ocrconfig -export -s online, and use -import option to restore the contents back.
With Oracle RAC 11g Release 1, you can do a manaual backup of the OCR with the command:
# ocrconfig -manualbackup 


 Q How do you backup voting disk?


#dd if=voting_disk_name of=backup_file_name


 Q How do I identify the voting disk location ?

#crsctl query css votedisk


 Q How do I identify the OCR file location ?


check /var/opt/oracle/ocr.loc or /etc/ocr.loc ( depends upon platform)
or
#ocrcheck


 Q Is ssh required for normal Oracle RAC operation ?


"ssh" are not required for normal Oracle RAC operation. However "ssh" should be enabled for Oracle RAC and patchset installation.



 Q What is the purpose of Private Interconnect ?


Clusterware uses the private interconnect for cluster synchronization (network heartbeat) and daemon communication between the the clustered nodes. This communication is based on the TCP protocol.
RAC uses the interconnect for cache fusion (UDP) and inter-process communication (TCP). Cache Fusion is the remote memory mapping of Oracle buffers, shared between the caches of participating nodes in the cluster. 



 Q Why do we have a Virtual IP (VIP) in Oracle RAC?


Without using VIPs or FAN, clients connected to a node that died will often wait for a TCP timeout period (which can be up to 10 min) before getting an error. As a result, you don't really have a good HA solution without using VIPs.
When a node fails, the VIP associated with it is automatically failed over to some other node and new node re-arps the world indicating a new MAC address for the IP. Subsequent packets sent to the VIP go to the new node, which will send error RST packets back to the clients. This results in the clients getting errors immediately



 Q What do you do if you see GC CR BLOCK LOST in top 5 Timed Events in AWR Report? 


This is most likely due to a fault in interconnect network.
Check netstat -s
if you see "fragments dropped" or "packet reassemblies failed" , Work with your system administrator find the fault with network. 


 Q How many nodes are supported in a RAC Database?


10g Release 2, support 100 nodes in a cluster using Oracle Clusterware, and 100 instances in a RAC database.



 Q Srvctl cannot start instance, I get the following error PRKP-1001 CRS-0215, however sqlplus can start it on both nodes? How do you identify the problem?



Set the environmental variable SRVM_TRACE to true.. And start the instance with srvctl. Now you will get detailed error stack.



 Q what is the purpose of the ONS daemon?

The Oracle Notification Service (ONS) daemon is an daemon started by the CRS clusterware as part of the nodeapps. There is one ons daemon started per clustered node.
The Oracle Notification Service daemon receive a subset of published clusterware events via the local evmd and racgimon clusterware daemons and forward those events to application subscribers and to the local listeners.


This in order to facilitate:

a. the FAN or Fast Application Notification feature or allowing applications to respond to database state changes.
b. the 10gR2 Load Balancing Advisory, the feature that permit load balancing accross different rac nodes dependent of the load on the different nodes. The rdbms MMON is creating an advisory for distribution of work every 30seconds and forward it via racgimon and ONS to listeners and applications.



 Q How do users connect to database in an Oracle RAC environment?



Users can access a RAC database using a client/server configuration or through one or more middle tiers, with or without connection pooling. Users can use oracle services feature to connect to database.



 Q What is the use of a service in Oracle RAC environment?



Applications should use the services feature to connect to the Oracle database. Services enable us to define rules and characteristics to control how users and applications connect to database instances.



 Q What are the characteristics controlled by Oracle services feature?



The characteristics include a unique name, workload balancing and failover options, and high availability characteristics.


 Q What is a voting disk?


A voting disk is a file that manages information about node membership.



 Q What are the administrative tasks involved with voting disk?


Following administrative tasks are performed with the voting disk :

1) Backing up voting disks

2) Recovering Voting disks

3) Adding voting disks

4) Deleting voting disks

5) Moving voting disks


 Q How do we backup voting disks?


1) Oracle recommends that you back up your voting disk after the initial cluster creation and after we complete any node addition or deletion procedures.

2) First, as root user, stop Oracle Clusterware (with the crsctl stop crs command) on all nodes. Then, determine the current voting disk by issuing the following command:

crsctl query votedisk css

3) Then, issue the dd or ocopy command to back up a voting disk, as appropriate.

Give the syntax of backing up voting disks:-

On Linux or UNIX systems:

dd if=voting_disk_name of=backup_file_name

where,

voting_disk_name is the name of the active voting disk

backup_file_name is the name of the file to which we want to back up the voting disk contents

On Windows systems, use the ocopy command:

ocopy voting_disk_name backup_file_name


 Q What is the Oracle Recommendation for backing up voting disk?

Oracle recommends us to use the dd command to backup the voting disk with a minimum block size of 4KB.



 Q How do you restore a voting disk?

To restore the backup of your voting disk, issue the dd or ocopy command for Linux and UNIX systems or ocopy for Windows systems respectively.

On Linux or UNIX systems:

dd if=backup_file_name of=voting_disk_name

On Windows systems, use the ocopy command:

ocopy backup_file_name voting_disk_name

where,

backup_file_name is the name of the voting disk backup file

voting_disk_name is the name of the active voting disk



 Q How can we add and remove multiple voting disks?

If we have multiple voting disks, then we can remove the voting disks and add them back into our environment using the following commands, where path is the complete path of the location where the voting disk resides:

crsctl delete css votedisk path

crsctl add css votedisk path


 Q How do we stop Oracle Clusterware?When do we stop it?

Before making any modification to the voting disk, as root user, stop Oracle Clusterware using the crsctl stop crs command on all nodes.



 Q How do we add voting disk?

To add a voting disk, issue the following command as the root user, replacing the path variable with the fully qualified path name for the voting disk we want to add:

crsctl add css votedisk path -force


 Q How do we move voting disks?

To move a voting disk, issue the following commands as the root user, replacing the path variable with the fully qualified path name for the voting disk we want to move:

crsctl delete css votedisk path -force

crsctl add css votedisk path -force


 Q How do we remove voting disks?

To remove a voting disk, issue the following command as the root user, replacing the path variable with the fully qualified path name for the voting disk we want to remove:

crsctl delete css votedisk path -force


 Q What should we do after modifying voting disks?

After modifying the voting disk, restart Oracle Clusterware using the crsctl start crs command on all nodes, and verify the voting disk location using the following command:

crsctl query css votedisk



 Q When can we use -force option?

If our cluster is down, then we can include the -force option to modify the voting disk configuration, without interacting with active Oracle Clusterware daemons. However, using the -force option while any cluster node is active may corrupt our configuration.