********************************************************************************************************************************************************************* Real Cluster Applications (RAC) Questions & Answers ********************************************************************************************************************************************************************* 1) What is RAC? What is the use of RAC? In Real Application Clusters environments, all nodes concurrently execute transactions against the same database. Real Application Clusters coordinates each node’s access to the shared data to provide consistency and integrity. 1. 100% uptime 2. Performance 3. Scalability 2) What is cache fusion? Cache fusion is nothing but a mapping of remote memory of oracle buffers, which is shared between the caches participating nodes in the cluster. It is very easy to gain the block image from the instance that contain the block in its SGA instead of reading from the disk, this happens when the block of data is read from data file by an instance in the cluster and when another instance require the same block. 3) What are the components of clusterware? Oracle cluster registry (OCR) Voting Disk 4) What is the difference between instance and crash recovery? The crash recovery takes place during the startup.when an instance, breaks up in a single node database. The same recovery is performed in the RAC environment by the surviving nodes, which is called as an instance recovery. 5) What is the split brain? When nodes of the database in a cluster can’t communicate with each other, they modify the data blocks and may continue to process independently. If more than one instance modify the same block, locking or synchronization of the blocks of the data does not occur and it may happen that the blocks get overwritten by others in the cluster. This process is called split brain. 6) What is GRD? GRD is the Global Resource Directory. The GRD is used by the GES and GCS to maintain the records of each cached block and each datafile. This process is known as cache fusion and can be used in data integrity. 7) What is an interconnect network? It is a private network, which connects all the servers in a cluster. It uses the multiple switches which are accessed by only the nodes in the cluster. 8) What are Oracle Clusterware/Daemon processes and what they do? ocssd, crsd, evmd, oprocd, racgmain, racgimon 9) What are the special background processes for RAC? DIAG, LCKn, LMD, LMSn, LMON 10) What are the new features in 11g (R2) RAC? Grid & ASM, Voting disk & ocrfile, SCAN, By using srvctl, we can mange diskgroups, home, ons, eons, filesystem, srvpool, server, scan, scan_listener, gns, vip, oc4j, GSD 11) What is OCR file? RAC configuration information repository that manages information about the cluster node list and instance-to-node mapping information. The OCR also manages information about Oracle Clusterware resource profiles for customized applications. 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. The daemon OCSSd manages the configuration info in OCR and maintains the changes to cluster in the registry. 12) What is Voting file/disk and how many files should be there? Voting Disk File is a file on the shared cluster system or a shared raw device file. Oracle Clusterware uses the voting disk to determine which instances are members of a cluster. Voting disk is akin to the quorum disk, which helps to avoid the split-brain syndrome. 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. 13) Who will manage OCR files? cssd will manage OCR. 14) Mention what is cluster? A cluster is referred to a group of independent, but connected servers that behaves as a single system. 15) Mention what is Oracle Real Application Clusters? RAC or Real Application Cluster is a component of the database product that enables the database to be installed across multiple servers. Oracle RAC uses Oracle Clusterware for the infrastructure to bind multiple servers, so they operate as a single system. 16) Mention what are the main components of an Oracle RAC system? Shared disk system, Oracle Clusterware, Cluster Interconnects & Oracle Kernel Components 17) Mention what are the benefits of Oracle RAC? Business Continuity and High Availability Workload Management with least expense Agility and Scalability System management and Standardized deployment 18) Mention what is new feature in Oracle ASM 12c? The new feature added in Oracle ASM 12c is Oracle Flex ASM. Its a new ASM deployment model which increases instance database availability and reduces the Oracle ASM related resource consumption. 19) Mention what are the key characteristics of RAC or why to use RAC? Reliability, Error Detection, Recoverability & Continuous Operations 20) Mention in RAC what files should be created on shared storage? In RAC ControlFiles, Spfiles, Redolog files, and Datafiles should be created on shared storage. 21) What is a virtual IP address or VIP? A virtual IP address or VIP is an alternate IP address that the client connections use instead of the standard public IP address. To configure VIP 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. 22) 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. 23) 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. 24) How many voting disks are you maintaining ? By default Oracle will create 3 voting disk files in ASM. 25) Why we need to keep odd number of voting disks ? Oracle expects that you will configure at least 3 voting disks for redundancy purposes. You should always configure an odd number of voting disks >= 3. This is because loss of more than half your voting disks will cause the entire cluster to fail. 26) 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 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. 26) What is SCAN? (11gR2 feature) 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. 27) In 2 node RAC, how many NIC’s are r using ? 2 network cards on each clusterware node Network Card 1 (with IP address set 1) for public network Network Card 2 (with IP address set 2) for private network 28) In 2 node RAC, how many IP’s are r using ? 6 – 3 set of IP address # eth1-Public: 2 # eth0-Private: 2 # VIP: 2 29) How to find IP’s information in RAC ? Edit the /etc/hosts file 1) vi /etc/hosts & 2) cat /etc/hosts 30) What is difference between RAC ip addresses ? Public IP adress is the normal IP address typically used by DBA and SA to manage storage, system and database. Private IP address is used only for internal clustering processing (Cache Fusion) VIP is used by database applications to enable fail over when one cluster node fails. 31) How you check the health of Your RAC Database? crsctl check crs 32) How you will backup your RAC Database? An RAC Database consists of 1)OCR, 2)Voting disk & 3)Database files, controlfiles, redolog files & Archive log files 33) What is the use of cluster interconnect? Cluster interconnect is used by the Cache fusion for inter instance communication 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. 34) 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 35) How do we verify that RAC instances are running? SQL>select * from V$ACTIVE_INSTANCES; 36) 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. 37) What are the three greatest benefits that RAC provides? Availability, Scalability, & Ability 38) List Key benefits of ASM? Stripes files rather than logical volumes Provides redundancy on a file basis Enables online disk reconfiguration and dynamic rebalancing Supports reading from mirrored copy instead of primary copy for extended clusters Is automatically installed as part of the Grid Infrastructure 39) 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 40) What is ASM in Oracle? Oracle ASM is Oracle’s volume manager specially designed for Oracle database data. It is available since Oracle database version 10g and many improvements have been made in versions 11g release 1 and 2. 41) What kind of files can be stored on ASM Diskgroup? * Control files * Datafiles, temporary datafiles, and datafile copies * SPFILEs * Online redo logs, archive logs, * RMAN backups * Disaster recovery configurations * Change tracking bitmaps * Data Pump dumpsets 42) What is the use of RAC Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. 43) What are various IPs used in RAC? Or How may IPs we need in RAC? Public IP, Private IP, Virtual IP, SCAN IP 44) What is the use of SCAN IP (SCAN name) and will it provide load balancing? Single Client Access Name (SCAN) is 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. 45) How many SCAN listeners will be running? Three SCAN listeners only. 46) What are nodeapps? VIP, listener, ONS, GSD 47) What are Oracle Cluster ware/Daemon processes and what they do? OCSSD, CRSD, EVMD 48) What are the special background processes for RAC? DIAG, LCKn, LMD, LMSn, LMON 49) What is the cache fusion? Transferring of data between RAC instances by using private network. 50) What are various IPs used in RAC? Or How may IPs we need in RAC? Public IP, Private IP, Virtual IP, SCAN IP 51) How many SCAN listeners will be running? Three SCAN listeners only. 52) What are node apps? VIP, listener, ONS, GSD 53) What utility is used to start DB/instance? srvctl start database –d database_name srvctl start instance –d database_name –i instance_name ========================================================================THE END===============================================================================