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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Downgrading Grid Infrastructure from 12.1.0.2 to 11.2.0.4

In the last article, we performed downgrade of Oracle RAC Database from 12c to 11gR2. In this article, we are going to downgrade Oracle Grid Infrastructure from 12c (12.1.0.2) to 11gR2 (11.2.0.4) which contains two nodes ( node 1 & node 2). Before doing CRS downgrade we need to take backup of following files : Take tar […]

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Downgrading a RAC database from 12.1.0.2 to 11.2.0.4

In the last article, we performed downgrade of Oracle Standalone Database from 12c to 11gR2. In this article, we can downgrade the 2 node RAC 12.1.0.2 database to 11.2.0.4, downgraded the database only and not the grid home. Assume all commands are being run on node 1, any commands that need to be run on node 2 […]

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Downgrade Oracle Database from 12c to 11gR2

We have already upgraded Oracle Database11gR2 to 12c, the whole process is still relatively smooth, although some of the previous version of the upgrade is not the same, but the overall difficulty is not too large, because of too many different features, greatly extended the upgrade time. But for Oracle 12c back to the previous […]

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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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Killable Processes in Oracle Database

A multiprocess Oracle database uses some additional processes called background processes. The background processes perform maintenance tasks required to operate the database and to maximize performance for multiple users. Mandatory Background Processes Optional Background Processes Slave Processes There are few processes which we can kill without terminating the instance. Killable: ARCn: Redo log archivers CJQn: Job […]

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Oracle HCM Cloud Concepts – Part 1 (Colored E-Book)

A handy reference guide explaining core concepts of Oracle HCM Cloud Application. All the worked out examples have been performed in a SaaS Deployment but very well applies for an On-Premise of Hybrid Deployment Model too. Topics covered includes HCM Data Loader, Comparison of HCM Data Loader with File Based Data Loader, Creating OTBI Analysis, […]

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