1. What is the major difference between 10g and 11g RAC?Well, there is not much difference between 10g and 11gR (1) RAC.But there is a significant difference in 11gR2.Prior to 11gR1(10g) RAC, the following were managed by Oracle CRS Databases Instances Applications Node Monitoring Event Services High AvailabilityFrom 11gR2(onwards) its completed HA stack managing and providing the following resources as like the other cluster software like VCS etc. Databases Instances Applications Cluster Management Node Management Event Services High Availability Network Management (provides DNS/GNS/MDNSD services on behalf of other traditional services) and SCAN Single Access Client Naming method, HAIP Storage Management (with help of ASM and other new ACFS filesystem) Time synchronization (rather depending upon traditional NTP) Removed OS dependent hang checker etc, manages with own additional monitor process2. What are Oracle Cluster Components?Cluster Interconnect (HAIP)Shared Storage (OCR/Voting Disk)Clusterware software3. What are Oracle RAC Components?VIP, Node apps etc.4. What are Oracle Kernel Components (nothing but how does Oracle RAC database differs than Normal single instance database in terms of Binaries and process)Basically Oracle kernel need to switched on with RAC On option when you convert to RAC, that is the difference as it facilitates few RAC bg process like LMON,LCK,LMD,LMS etc.To turn on RAC# link the oracle libraries$ cd $ORACLE_HOME/rdbms/lib$ make -f ins_rdbms.mk rac_on# rebuild oracle$ cd $ORACLE_HOME/bin$ relink oracleOracle 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:ACMSAtomic Controlfile to Memory Service (ACMS)GTX0-jGlobal Transaction ProcessLMONGlobal Enqueue Service MonitorLMDGlobal Enqueue Service DaemonLMSGlobal CacheService ProcessLCK0Instance Enqueue ProcessRMSnOracle RAC Management Processes (RMSn)RSMNRemote Slave Monitor5. What is Clusterware?Software that provides various interfaces and services for a cluster. Typically, this includes capabilities that: Allow the cluster to be managed as a whole Protect the integrity of the cluster Maintain a registry of resources across the cluster Deal with changes to the cluster Provide a common view of resources6. What are the background process that exists in 11gr2 and functionality?Process NameFunctionality

crsdThe CRS daemon (crsd) manages cluster resources based on configuration information that is stored in Oracle Cluster Registry (OCR) for each resource. This includes start, stop, monitor, and failover operations. The crsd process generates events when the status of a resource changes.

cssdCluster Synchronization Service (CSS): Manages the cluster configuration by controlling which nodes are members of the cluster and by notifying members when a node joins or leaves the cluster. If you are using certified third-party clusterware, then CSS processes interfaces with your clusterware to manage node membership information. CSS has three separate processes: the CSS daemon (ocssd), the CSS Agent (cssdagent), and the CSS Monitor (cssdmonitor). The cssdagent process monitors the cluster and provides input/output fencing. This service formerly was provided by Oracle Process Monitor daemon (oprocd), also known as OraFenceService on Windows. A cssdagent failure results in Oracle Clusterware restarting the node.

diskmonDisk Monitor daemon (diskmon): Monitors and performs input/output fencing for Oracle Exadata Storage Server. As Exadata storage can be added to any Oracle RAC node at any point in time, the diskmon daemon is always started when ocssd is started.

evmdEvent Manager (EVM): Is a background process that publishes Oracle Clusterware events

mdnsdMulticast domain name service (mDNS): Allows DNS requests. The mDNS process is a background process on Linux and UNIX, and a service on Windows.

gnsdOracle Grid Naming Service (GNS): Is a gateway between the cluster mDNS and external DNS servers. The GNS process performs name resolution within the cluster.

onsOracle Notification Service (ONS): Is a publish-and-subscribe service for communicating Fast Application Notification (FAN) events

oraagentoraagent: Extends clusterware to support Oracle-specific requirements and complex resources. It runs server callout scripts when FAN events occur. This process was known as RACG in Oracle Clusterware 11g Release 1 (11.1).

orarootagentOracle root agent (orarootagent): Is a specialized oraagent process that helps CRSD manage resources owned by root, such as the network, and the Grid virtual IP address

oclskdCluster kill daemon (oclskd): Handles instance/node evictions requests that have been escalated to CSS

gipcdGrid IPC daemon (gipcd): Is a helper daemon for the communications infrastructure

ctssdCluster time synchronisation daemon(ctssd) to manage the time syncrhonization between nodes, rather depending on NTP

7. Under which user or owner the process will start?ComponentName of the ProcessOwner

Oracle High Availability Serviceohasdinit, root

Cluster Ready Service (CRS)Cluster Ready Servicesroot

Cluster Synchronization Service (CSS)ocssd,cssd monitor, cssdagentgrid owner

Event Manager (EVM)evmd, evmloggergrid owner

Cluster Time Synchronization Service (CTSS)octssdroot

Oracle Notification Service (ONS)ons, eonsgrid owner

Oracle Agentoragentgrid owner

Oracle Root Agentorarootagentroot

Grid Naming Service (GNS)gnsdroot

Grid Plug and Play (GPnP)gpnpdgrid owner

Multicast domain name service (mDNS)mdnsdgrid owner

8. What is startup sequence in Oracle 11g RAC? 11g RAC startup sequence?Click here to know more details9. As you said Voting & OCR Disk resides in ASM Diskgroups, but as per startup sequence OCSSD starts first before than ASM, how is it possible?How does OCSSD starts if voting disk & OCR resides in ASM Diskgroups?You might wonder how CSSD, which is required to start the clustered ASM instance, can be started if voting disks are stored in ASM? This sounds like a chicken-and-egg problem: without access to the voting disks there is no CSS, hence the node cannot join the cluster. But without being part of the cluster, CSSD cannot start the ASM instance. To solve this problem the ASM disk headers have new metadata in 11.2: you can use kfed to read the header of an ASM disk containing a voting disk. The kfdhdb.vfstart and kfdhdb.vfend fields tell CSS where to find the voting file. This does not require the ASM instance to be up. Once the voting disks are located, CSS can access them and joins the cluster.Source:Pro Oracle Database 11g RAC on Linux- Martin Bach Amazon.com10. How does SCAN works?

1. Client Connected through SCAN name of the cluster (remember all three IP addresses round robin resolves to same Host name (SCAN Name), here in this case our scan name is cluster01-scan.cluster01.example.com2. The request reaches toDNS serverin your corp and then resolves to one of the node out of three. a. If GNS (Grid Naming service or domain is configured) that is a subdomain configured in the DNS entry for to resolve cluster address the request will be handover to GNS (gnsd)3. Here in our case assume there is no GNS, now the with the help of SCAN listeners where end points are configured to database listener.4. Database Listeners listen the request and then process further.5. In case of node addition, Listener 4, client need not to know or need not change any thing from their tns entry (address of 4thnode/instance) as they just using scan IP.6. Same case even in the node deletion.11. What is GNS?Grid Naming service is alternative service to DNS , which will act as a sub domain in your DNS but managed by Oracle, with GNS the connection is routed to the cluster IP and manages internally.12. What is GPNP?Grid Plug and Play along with GNS provide dynamicIn previous releases, adding or removing servers in a cluster required extensive manual preparation.InOracle Database11gRelease 2, GPnP allows each node to perform the following tasks dynamically: Negotiating appropriate network identities for itself Acquiring additional information from a configuration profile Configuring or reconfiguring itself using profile data, making host names and addresses resolvable on the networkFor example a domain should contain Cluster name:cluster01 Network domain:example.com GPnP domain:cluster01.example.comTo add a node, simply connect the server to the cluster and allow the cluster to configure the node.To make it happen, Oracle uses the profile located in $GI_HOME/gpnp/profiles/peer/profile.xml which contains the cluster resources, for example disk locations of ASM. etc.So this profile will be read local or from the remote machine when plugged into cluster and dynamically added to cluster.13. What are the file types that ASM support and keep in disk groups?Control filesFlashback logsData Pump dump sets

Data filesDB SPFILEData Guard configuration

Temporary data filesRMAN backup setsChange tracking bitmaps

Online redo logsRMAN data file copiesOCR files

Archive logsTransport data filesASM SPFILE

14. List Key benefits of ASM? Stripes files rather than logical volumes Provides redundancy on a file basis Enables online disk reconfiguration and dynamic rebalancing Reduces the time significantly to resynchronize a transient failure by tracking changes while disk is offline Provides adjustable rebalancing speed Is cluster-aware Supports reading from mirrored copy instead of primary copy for extended clusters Is automatically installed as part of the Grid Infrastructure15. List key benefits of Oracle Grid Infrastructure?16. List some of the background process that used in ASM?ProcessDescription

RBALOpens all device files as part of discovery and coordinates the rebalance activity

ARBnOne or more slave processes that do the rebalance activity

GMONResponsible for managing the disk-level activities such as drop or offline and advancing the ASM disk group compatibility

MARKMarks ASM allocation units as stale when needed

OnnnOne or more ASM slave processes forming a pool of connections to the ASM instance for exchanging messages

PZ9nOne or more parallel slave processes used in fetching data on clustered ASM installation from GV$ views

13. What is node listener?In 11gr2 the listeners will run from Grid Infrastructure software home The node listener is a process that helps establish network connections from ASM clients to the ASM instance. Runs by default from the Grid $ORACLE_HOME/bin directory Listens on port 1521 by default Is the same as a database instance listener Is capable of listening for all database instances on the same machine in addition to the ASM instance Can run concurrently with separate database listeners or be replaced by a separate database listener Is named tnslsnr on the Linux platform15. What is SCAN listener?A scan listener is something that additional to node listener which listens the incoming db connection requests from the client which got through the scan IP, it got end points configured to node listener where it routes the db connection requests to particular node listener.16. What is the difference between CRSCTL and SRVCTL?crsctl manages clusterware-related operations: Starting and stopping Oracle Clusterware Enabling and disabling Oracle Clusterware daemons Registering cluster resourcessrvctl manages Oracle resourcerelated operations: Starting and stopping database instances and services Also from 11gR2 manages the cluster resources like network,vip,disks etc17. How to control Oracle Clusterware?To start or stop Oracle Clusterware on a specific node:# crsctl stop crs# crsctl start crsTo enable or disable Oracle Clusterware on a specific node:# crsctl enable crs# crsctl disable crs19. How to check the cluster (all nodes) status?To check the viability of Cluster Synchronization Services (CSS) across nodes:$ crsctl check clusterCRS-4537: Cluster Ready Services is onlineCRS-4529: Cluster Synchronization Services is onlineCRS-4533: Event Manager is online20. How to check the cluster (one node) status?$ crsctl check crsCRS-4638: OracleHigh AvailabilityServices is onlineCRS-4537: Cluster Ready Services is onlineCRS-4529: Cluster Synchronization Services is onlineCRS-4533: Event Manager is online21. How to find Voting Disk location?To determine the location of the voting disk:# crsctl query css votedisk## STATE File Universal Id File Name Disk group - -1. ONLINE 8c2e45d734c64f8abf9f136990f3daf8 (ASMDISK01) [DATA]2. ONLINE 99bc153df3b84fb4bf071d916089fd4a (ASMDISK02) [DATA]3. ONLINE 0b090b6b19154fc1bf5913bc70340921 (ASMDISK03) [DATA]Located 3 voting disk(s).22. How to find Location of OCR? cat /etc/oracle/ocr.lococrconfig_loc=+DATAlocal_only=FALSE #OCRCHECK (also about OCR integrity)23. List some background process that used in ASM Instances?ProcessDescription

RBALOpens all device files as part of discovery and coordinates the rebalance activity

ARBnOne or more slave processes that do the rebalance activity

GMONResponsible for managing the disk-level activities such as drop or offline and advancing the ASM disk group compatibility

MARKMarks ASM allocation units as stale when needed

OnnnOne or more ASM slave processes forming a pool of connections to the ASM instance for exchanging messages

PZ9nOne or more parallel slave processes used in fetching data on clustered ASM installation from GV$ views

24. What are types of ASM Mirroring?Disk Group TypeSupported MirroringLevelsDefault MirroringLevel

External redundancyUnprotected (None)Unprotected (None)

Normal redundancyTwo-wayThree-wayUnprotected (None)Two-way

High redundancyThree-wayThree-way

25. What is ASM Striping?ASM can use variable size data extents to support larger files, reduce memory requirements, and improve performance.Each data extent resides on an individual disk.Data extents consist of one or more allocation units.The data extent size is: Equal to AU for the first 20,000 extents (019999) Equal to 4 AU for the next 20,000 extents (2000039999) Equal to 16 AU for extents above 40,000ASM stripes files using extents with a coarse method for load balancing or a fine method to reduce latency. Coarse-grained striping is always equal to the effective AU size. Fine-grained striping is always equal to 128 KB.26. How many ASM Diskgroups can be created under one ASM Instance?ASM imposes the following limits: 63 disk groups in a storage system 10,000 ASM disks in a storage system Two-terabyte maximum storage for each ASM disk (non-Exadata) Four-petabyte maximum storage for each ASM disk (Exadata) 40-exabyte maximum storage for each storage system 1 millionfiles for each disk group ASM file size limits (database limit is 128 TB):1. External redundancy maximum file size is 140 PB.2. Normal redundancy maximum file size is 42 PB.3. High redundancy maximum file size is 15 PB.27. How to find the cluster network settings?To determine the list of interfaces available to the cluster:$ oifcfg iflist p -nTo determine the public and private interfaces that have been configured:$ oifcfg getifeth0 192.0.2.0 global publiceth1 192.168.1.0 global cluster_interconnectTo determine the Virtual IP (VIP) host name, VIP address, VIP subnet mask, and VIP interface name:$ srvctl config nodeapps -aVIP exists.:host01VIP exists.: /192.0.2.247/192.0.2.247/255.255.255.0/eth028. How to change Public or VIP Address in RAC Cluster?Click here for details29. How to change Cluster interconnect in RAC?On a single node in the cluster, add the new global interface specification:$ oifcfg setif -global eth2/192.0.2.0:cluster_interconnectVerify the changes with oifcfg getif and then stop Clusterware on all nodes by running the following command as root on each node:# oifcfg getif# crsctl stop crsAssign the network address to the new network adapters on all nodes using ifconfig:#ifconfig eth2192.0.2.15 netmask 255.255.255.0 broadcast 192.0.2.255Remove the former adapter/subnet specification and restart Clusterware:$ oifcfgdelif -global eth1/192.168.1.0# crsctl start crs30. Managing or Modifying SCAN in Oracle RAC?To add a SCAN VIP resource:$ srvctl add scan -ncluster01-scanTo remove Clusterware resources from SCAN VIPs:$ srvctl remove scan [-f]To add a SCAN listener resource:$ srvctl add scan_listener$ srvctl add scan_listener -p 1521To remove Clusterware resources from all SCAN listeners:$ srvctl remove scan_listener [-f]31. How to check the node connectivity in Oracle Grid Infrastructure?$ cluvfy comp nodecon -n all verbose32. Can I stop all nodes in one command? Meaning that stopping whole cluster ?In 10g its not possible, where in 11g it is possible[root@pic1]# crsctl start cluster -all[root@pic2]# crsctl stop cluster all33. What is OLR? Which of the following statements regarding the Oracle Local Registry (OLR) is true?1.Each cluster node has a local registry for node-specific resources.2.The OLR should be manually created after installing Grid Infrastructure on each node in the cluster.3.One of its functions is to facilitate Clusterware startup in situations where the ASM stores the OCR and voting disks.4.You can check the status of the OLR using ocrcheck.34. What isrunfixup.sh script in Oracle Clusterware 11g release 2 installationWith 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.35. How to stop whole cluster with single commandcrsctl stop cluster (possible only from 11gr2), please note crsctl commands becomes global now, if you do not specify node specifically the command executed globally for examplecrsctl stop crs (stops in all crs resource in all nodes)crsctl stop crs n FAN > FCFONS -> send/receive messages on local and remote nodes.FAN -> uses ONS to notify other processes about changes in configuration of service levelFCF -> uses FAN information working with conection pools JAVA and others.42. Can you add voting disk online? Do you need voting disk backup?Yes, as per documentation, if you have multiple voting disk you can add online, but if you have only one voting disk , by that cluster will be down as its lost you just need to start crs in exclusive mode and add the votedisk usingcrsctl add votedisk 43. You have lost OCR disk, what is your next step?The cluster stack will be down due to the fact that cssd is unable to maintain the integrity, this is true in 10g, From 11gR2 onwards, the crsd stack will be down, the hasd still up and running. You can add the ocr back by restoring theautomatic backupor import the manual backup,Read complete steps here44. What happens when ocssd fails, what is node eviction? how does node eviction happens? For all answer will be same.Read here45. What is virtual IP and how does it works?Read here46. Describe some rac wait events you experienced?Oracle RAC Wait eventsand this table,

47. Can you modify VIP address after your cluster installation?Yes,read here48. How do you interpret AWR report in RAC instances, what sections in awr report for rac instances are most important?Read here.Update 12-May-2013, Some practical questions added here1. Viewing Contents in OCR/Voting disksThere are three possible ways to view the OCR contents.a.OCRDUMP (or)b.crs_stat -p (or)c.By using strings.Voting disk contents are not persistent and are not required to view the contents, because the voting disk contents will be overwritten. if still need to view, strings are used. 2. Server pools Read in my blog3. Verifying Cluster Interconnect Cluster interconnects can be verified by:i.oifcfg getifii.From AWR Report.iii.show parameter cluster_interconnectiv.srvctl config network4. Does scan IP required or we can disable it SCAN IP can be disabled if not required. However SCAN IP is mandatory during the RAC installation. Enabling/disabling SCAN IP is mostly used in oracle apps environment by the concurrent manager (kind of job scheduler in oracle apps). To disable the SCAN IP,i.Do not use SCAN IP at the client end.ii.Stop scan listener srvctl stop scan_listeneriii.Stop scan srvctl stop scan (this will stop the scan vip's)iv.Disable scan and disable scan listener srvctl disable scan5. Migrating to new Diskgroup scenariousa.Case 1: Migrating disk group from one storage to other with same name 1. Consider the disk group is DATA, 2. Create new disks in DATA pointing towards the new storage (EMC), a) Partioning provisioning done by storage and they give you the device name or mapper like /dev/mapper/asakljdlas 3. Add the new disk to diskgroup DATA a) Alter diskgroup data add disk '/dev/mapper/asakljdlas' 3. drop the old disks from DATA with which rebalancing is done automatically. If you want you can the rebalance by alter system set asm_power_limit =12 for full throttle. alter diskgroup data drop disk 'path to hitachi storage' Note: you can get the device name in v$asm_disk in path column. 4. Request SAN team to detach the old Storage (HITACHI).

b.Case 2: Migrating disk group from one to another with different diskgroup name. 1) Create the Disk group with new name in the new storage. 2) Create the spfile in new diskgroup and change the parameter scope = spfile for control files etc. 3) Take a control file backup in format +newdiskgroup 4) Shutdown the db, startup nomount the database 5) restore the control file from backup (now the control will restore to new diskgroup) 6) Take the RMAN backup as copy of all the databases with new format. RMAN> backup database as copy format '+newdiskgroup name' ; 3) RMAN> Switch database to copy. 4) Verify dba_data_files,dba_temp_files, v$log that all files are pointing to new diskgroup name.

c.Case 3: Migrating disk group to new storage but no additional diskgroup given 1) Take the RMAN backup as copy of all the databases with new format and place it in the disk. 2) Prepare rename commands from v$log ,v$datafile etc (dynamic queries) 3) Take a backup of pfile and modify the following referring to new diskgroup name .control_files.db_create_file_dest.db_create_online_log_dest_1.db_create_online_log_dest_2.db_recovery_file_des 4) stop the database 5) Unmount the diskgroup asmcmd umount ORA_DATA 6) use asmcmd renamedg (11gr2 only) command to rename to new diskgroup renamedg phase=both dgname=ORA_DATA newdgname=NEW_DATA verbose=true 7) mount the diskgroup asmcmd mount NEW_DATA 8) start the database in mount with new pfile taken backup in step 3 9) Run the rename file scripts generated at step2 9) Add the diskgroup to cluster the cluster (if using rac) srvctl modify database -d orcl -p +NEW_FRA/orcl/spfileorcl.ora srvctl modify database -d orcl -a "NEW_DATA" srvctl config database -d orcl srvctl start database -d orcl 10) Delete the old diskgroup from cluster crsctl delete resource ora.ORA_DATA.dg 11) Open the database.7. Database rename in RAC, what could be the checklist for you?a.Take the outputs of all the services that are running on the databases.b.set cluster_database=FALSEc.Drop all the services associated with the database.d.Stop the databasee.Startup mountf.Use nid to change the DB Name. Generic question, If using ASM the usual location for the datafile would be +DATA/datafile/OLDDBNAME/system01.dbf' Does NID changes this path too? to reflect the new db name? Yes it will, by using proper directory structure it will create a links to original directory structure. +DATA/datafile/NEWDBNAME/system01.dbf' this has to be tested, We dont have test bed, but thanks to Anji who confirmed it will

g.Change the parameters according to the new database nameh.Change the password file.i.Stop the database.j.Mount the databasek.Open database with Reset logsl.Create spfile from pfile.m.Add database to the cluster.n.Create the services that are dropped in prior to rename.o.Bounce the database.8.How to find the database in which particular service is attached to when you have a large number of databases running in the server, you cannot check one by one manuallyWrite a shell script to read the database name from oratab and iterate the loop taking inpt as DB name in srvctl to get the result.#!/bin/kshORACLE_HOME=PATH=$ORACLE_HOME/bin:$PATHLD_LIBRARY_PATH=${SAVE_LLP}:${ORACLE_HOME}/libexport TNS_ADMIN ORACLE_HOME PATH LD_LIBRARY_PATHfor INSTANCE in `cat /etc/oratab|grep -v "^#"|cut -f1 -d: -s`doexport ORACLE_SID=$INSTANCEecho `srvctl status service -d $INSTANCE -s $1| grep -i "is running"`done9. Difference between OHAS and CRSOHAS is complete cluster stack which includes some kernel level tasks like managing network,time synchronization, disks etc, where the CRS has the ability to manage the resources like database,listeners,applications, etc With both of this Oracle provides thehigh availability

Oracle RAC Interview Questions & Answers

1. Where are the Clusterware files stored on a RAC environment?The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file)2. Where are the database software files stored on a RAC environment?The base software is installed on each node of the cluster and thedatabase storage on the shared disks.3. What kind of storage we can use for the shared Clusterware files?- OCFS (Release 1 or 2)- raw devices- third party cluster file system such as GPFS or Veritas4. What kind of storage we can use for the RAC database storage?- OCFS (Release 1 or 2)- ASM- raw devices- third party cluster file system such as GPFS or Veritas5. What is a CFS?A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view.6. What is an OCFS2?The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real Application Cluster.7. Which files can be placed on an Oracle Cluster File System?- Oracle Software installation (Windows only)- Oracle files (controlfiles, datafiles, redologs, files described by the bfile datatype)- Shared configuration files (spfile)- OCR and voting disk- Files created by Oracle during runtimeNote: There are some platform specific limitations.8. Do you know another Cluster Vendor?HP Tru64 Unix, Veritas, Microsoft9. How is possible to install a RAC if we dont have a CFS?This is possible by using a raw device.10. What is a raw device?A raw device is a disk drive that does not yet have a file system set up. Raw devices are used for Real Application Clusters since they enable the sharing of disks.11. What is a raw partition?A raw partition is a portion of a physical disk that is accessed at the lowest possible level. A raw partition is created when an extended partition is created and logical partitions are assigned to it without any formatting. Once formatting is complete, it is called cooked partition.12. When to use CFS over raw?A CFS offers:- Simpler management- Use of Oracle Managed Files with RAC- Single Oracle Software installation- Autoextend enabled on Oracle datafiles- Uniform accessibility to archive logs in case of physical node failure- With Oracle_Home on CFS, when you apply Oracle patches CFS guarantees that the updated Oracle_Home is visible to all nodes in the cluster.Note: This option is very dependent on the availability of a CFS on your platform.13. When to use raw over CFS?- Always when CFS is not available or not supported by Oracle.- The performance is very, very important: Raw devices offer best performance without any intermediate layer between Oracle and the disk.Note: Autoextend fails on raw devices if the space is exhausted. However the space could be added online if needed.14. What CRS is?Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent set of system services for cluster environments. In Release 2, Oracle has renamed this product to Oracle Clusterware.15. What is VIP IP used for?It returns a dead connection IMMIDIATELY, when its primary node fails. Without using VIP IP, the clients have to wait around 10 minutes to receive ORA-3113: end of file on communications channel. However, using Transparent Application Failover (TAF) could avoid ORA-3113.16. Why we need to have configured SSH or RSH on the RAC nodes?SSH (Secure Shell,10g+) or RSH (Remote Shell, 9i+) allows oracle UNIX account connecting to another RAC node and copy/ run commands as the local oracle UNIX account.17. Is the SSH, RSH needed for normal RAC operations?No. SSH or RSH are needed only for RAC, patch set installation and clustered database creation.18. Do we have to have Oracle RDBMS on all nodes?Each node of a cluster that is being used for a clustered database will typically have the RDBMS and RAC software loaded on it, but not actual data files (these need to be available via shared disk).19. What are the restrictions on the SID with a RAC database? Is it limited to 5 characters?The SID prefix in 10g Release 1 and prior versions was restricted to five characters by install/ config tools so that an ORACLE_SID of up to max of 5+3=8 characters can be supported in a RAC environment. The SID prefix is relaxed up to 8 characters in 10g Release 2, see bug 4024251 for more information.20. Does Real Application Clusters support heterogeneous platforms?The Real Application Clusters do not support heterogeneous platforms in the same cluster.

21. Are there any issues for the interconnect when sharing the same switch as the public network by using VLAN to separate the network?RAC and Clusterware deployment best practices suggests that the interconnect (private connection) be deployed on a stand-alone, physically separate, dedicated switch. On big network the connections could be instable.22. What is the Load Balancing Advisory?To assist in the balancing of application workload across designated resources, Oracle Database 10g Release 2 provides the Load Balancing Advisory. This Advisory monitors the current workload activity across the cluster and for each instance where a service is active; it provides a percentage value of how much of the total workload should be sent to this instance as well as service quality flag.23. How many nodes are supported in a RAC Database?With 10g Release 2, we support 100 nodes in a cluster using Oracle Clusterware, and 100 instances in a RAC database. Currently DBCA has a bug where it will not go beyond 63 instances. There is also a documentation bug for the max-instances parameter. With 10g Release 1 the Maximum is 63.

24. What is the Cluster Verification Utiltiy (cluvfy)?The Cluster Verification Utility (CVU) is a validation tool that you can use to check all the important components that need to be verified at different stages of deployment in a RAC environment.25. What versions of the database can I use the cluster verification utility (cluvfy) with?The cluster verification utility is release with Oracle Database 10g Release 2 but can also be used with Oracle Database 10g Release 1.26. If I am using Vendor Clusterware such as Veritas, IBM, Sun or HP, do I still need Oracle Clusterware to run Oracle RAC 10g?Yes. When certified, you can use Vendor Clusterware however you must still install and use Oracle Clusterware for RAC. Best Practice is to leave Oracle Clusterware to manage RAC. For details see Metalink Note 332257.1 and for Veritas SFRAC see 397460.1.27. Is RAC on VMWare supported?Yes.28. What is hangcheck timer used for ?The hangcheck timer checks regularly the health of the system. If the system hangs or stop the node will be restarted automatically.There are 2 key parameters for this module:-> hangcheck-tick: this parameter defines the period of time between checks of system health. The default value is 60 seconds; Oracle recommends setting it to 30seconds.-> hangcheck-margin: this defines the maximum hang delay that should be tolerated before hangcheck-timer resets the RAC node.29. Is the hangcheck timer still needed with Oracle RAC 10g?Yes.30. What files can I put on Linux OCFS2?For optimal performance, you should only put the following files on Linux OCFS2:- Datafiles- Control Files- Redo Logs- Archive Logs- Shared Configuration File (OCR)- Voting File- SPFILE31. Is it possible to use ASM for the OCR and voting disk?No, the OCR and voting disk must be on raw or CFS (cluster file system).32. Can I change the name of my cluster after I have created it when I am using Oracle Clusterware?No, you must properly uninstall Oracle Clusterware and then re-install.33. What the O2CB is?The O2CB is the OCFS2 cluster stack. OCFS2 includes some services. These services must be started before using OCFS2 (mount/ format the file systems).34. What the OCR file is used for?OCR is a file that manages the cluster and RAC configuration.35. What the Voting Disk file is used for?The voting disk is nothing but a file that contains and manages information of all the node memberships.36. What is the recommended method to make backups of a RAC environment? RMAN to make backups of the database, dd to backup your voting disk and hard copies of the OCR file.37.What command would you use to check the availability of the RAC system?crs_stat -t -v (-t -v are optional)38.What is the minimum number of instances you need to have in order to create a RAC?You can create a RAC with just one server.39.Name two specific RAC background processesRAC processes are: LMON, LMDx, LMSn, LKCx and DIAG.40.Can you have many database versions in the same RAC?Yes, but Clusterware version must be greater than the greater database version.41. What was RAC previous name before it was called RAC?OPS: Oracle Parallel Server42. What RAC component is used for communication between instances?Private Interconnect.43. What is the difference between normal views and RAC views?A RAC view has the prefix G. For example, GV$SESSION instead of V$SESSION44. Which command will we use to manage (stop, start) RAC services in command-line mode?srvctl45. How many alert logs exist in a RAC environment?A- One for each instance.46. What are Oracle Clusterware ComponentsVoting 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 cluster47. How do you backup voting disk#dd if=voting_disk_name of=backup_file_name48. How do I identify the votingdisk location#crsctl query css votedisk49. How do I identify the OCR file locationcheck /var/opt/oracle/ocr.loc or /etc/ocr.loc ( depends upon platform)or#ocrcheck50. 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.

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