Rebootless node fencing in Oracle RAC

Oracle Grid Infrastructure 11.2.0.2 has many features including Cluster Node Membership, Cluster Resource Management, and Cluster Resources monitoring. One of the key areas where DBA need to have expert knowledge on how the cluster node membership works and how the cluster decides to take out node should there be a heartbeat network, voting disk or […]

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Types of Supplemental logging at Database level

Redo log files are generally used for instance recovery and media recovery. The data needed for such operations is automatically recorded in the redo log files. However, a redo-based application may require that additional column be logged in the redo log files. The process of logging these additional columns is called supplemental logging. There are two […]

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Node eviction in Oracle RAC

Node eviction is quite sometimes happening in Oracle RAC environment on any platform and troubleshooting and finding root cause for node eviction is very important for DBAs to avoid same in the future. There can be many reasons behind node eviction like , Network Heartbeat Missed Voting Heartbeat Missed CSSD Agent/ Monitor hung RDBMS instance […]

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Split Brain and Amnesia in Oracle RAC

Split Brain and Amnesia Two types of problems can arise from cluster partitions: split brain and amnesia. Split brain occurs when the cluster interconnect between hosts is lost and the cluster becomes partitioned into subclusters, and each subcluster believes that it is the only partition. A sub-cluster that is not aware of the other subclusters […]

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Oracle RAC Cache Fusion

Cache Fusion is one of the most Important concepts in Oracle RAC. As we know each and every instance of RAC cluster is having its own local buffer cache where it does cache functionality.But when multiple users are connected to different nodes , a need to access or lock a data block owned by other […]

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How GRD works in Oracle RAC

An Oracle RAC database has the same processes and memory structures as a single instance.Oracle database have additional process and memory structures that are specific to Oracle RAC.The global cache service and global enqueue service processes, and the global resource directory (GRD) collaborate to enable cache fusion. Global Resource Directory [GRD] : Cluster operations require […]

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How to increase number of database writer in Oracle Database

Database Writer Process (DBW) The database writer process (DBW) writes the contents of database buffers to data files. DBW processes write modified buffers in the database buffer cache to disk. Although one database writer process (DBW0) is adequate for most systems, you can configure additional processes—DBW1-DBW9, DBWa-DBWz and BW36-BW99—to improve write performance if your system […]

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Contention-Related Wait Events

Contention-Related Wait Events : It is common to see the gc cr block busy and gc current block busy wait events in Oracle RAC systems. These events occur when a consistent read or current block is needed from another instance yet it is taking some time to receive that block, and the sending of the […]

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Load-oriented oracle rac wait events

Load-oriented oracle RAC wait events : The load-oriented wait events indicate that a delay in processing has occurred in the GCS, which is usually caused by high load, CPU saturation and would have to be solved by additional CPUs, load-balancing, off loading processing to different times or a new cluster node. For the events mentioned, […]

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Message-Oriented Oracle RAC wait events

Message-Oriented Oracle RAC wait event The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. Instead, a global grant was given, enabling the requesting instance to read the block from disk or modify it. If the local instance is the resource master, the grant happens immediately.If […]

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