RAC

Command to Check Archivelog Size

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Oracle databases maintain a detailed history of all changes made to the database through archived redo logs, commonly known as archivelogs. These archivelogs are crucial for data recovery and are often managed by database administrators. Monitoring the size of archivelogs is essential to ensure optimal database performance and sufficient storage capacity. Here are some ways … Read more

Split Brain Syndrome in RAC

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Where two or more instances attempt to control a cluster database. Each node in this cluster are interconnected through private interconnect and end users connects to cluster through public network. When nodes are physically up and running and Database Instance on each of these servers is also running but private interconnect fails between two or … Read more

Voting Disk in Oracle RAC

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Voting disks manage information about node membership. Each voting disk must be accessible by all nodes in the cluster for nodes to be members of the cluster1. You can store OCR and voting disks on Oracle Automatic Storage Management (Oracle ASM)2. If it is stored in ASM, no need to configure manually as the files … Read more

Oracle Local Registry (OLR) in RAC

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Oracle Clusterware includes three components: voting disks, Oracle Cluster Registry (OCR), and Oracle Local Registry (OLR). ■ Voting disks manage information about node membership. Each voting disk must be accessible by all nodes in the cluster for nodes to be members of the cluster. ■ OCR manages Oracle Clusterware and Oracle RAC database configuration information. … Read more

Oracle Single Client Access Name (SCAN)

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Single Client Access Name (SCAN) is a feature used in Oracle Real Application Clusters environments that provides a single name for clients to access any Oracle Database running in a cluster. The benefit is that the client’s connect information does not need to change if you add or remove nodes or databases in the cluster. … Read more

Prerequisite check “CheckActiveFilesAndExecutables” failed.

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While trying to rollback the conflicting patch 18893947 applying patch 21967332 Following executables are active <dir>/product/12.1.0/12c/lib/libclntsh.so.12.1 The file libclntsh.so.12.1 will be present when emagent is running on the node and will periodically use the library libclntsh.so.11.1 Follow below steps: As root user 1. Run grep command to check and find process id active executable libclntsh.so … Read more

Oracle Clusterware Startup Sequence

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What is Oracle Clusterware – RAC ? Oracle Clusterware enables servers to communicate with each other, so that they appear to function as a collective unit. This combination of servers is commonly known as a “cluster”. Oracle Real Application Clusters known as Oracle RAC uses Oracle Clusterware as the infrastructure that binds multiple nodes that … Read more

Manual creation of SQL Profiles in Oracle Database

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SQL Profiles are a powerful tool to improve performance of SQL queries in your Oracle Database. A SQL profile is a database object that contains auxiliary statistics specific to a SQL statement. Conceptually, a SQL profile is to a SQL statement what object-level statistics are to a table or index. SQL profiles are created when a DBA … Read more

How To Run SQL Tuning Advisor

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When we run SQL tuning advisor against a SQL statement or sql_id, it provides tuning recommendations that can be used to improve performance. It might give suggestion to create few indexes or accepting a SQL profile. As we all know running a slow query is a major performance issue in the database also has the biggest challenge for DBA to resolve … Read more