In today’s article, we will cover the subject of “oracle rac node eviction”, which is perhaps one of the last thing a database administrator wants to see.
What is node eviction in Oracle Rac?
Eviction is a mechanism / process technology designed for Oracle Cluster. This technology separates the Nodes in the cluster, with or without critical problems, from the structure in order not to disturb the consistency and general cluster operation.
For example, if any node hangs on a cluster or thinks that it cannot be accessed for different reasons, Eviction will detach itself from the cluster structure and a quick reboot will occur for this node that appears to be problematic.
This process is registered by LMON with the error “ORA-29740 evicted by instance number”.
Its Main Causes are as follows and can be updated according to different cases.
- Network problems
- Memory (ram, swap, etc.) problems
- Excessive and prolonged load on the processor
- Bug 16876500 & Bug 14385860
How To Resolve Node Eviction in Oracle Rac?
Records to look for to fix the problem:
- All instance Alert Log records (cluster alert.log, asm alert.log)
- Ocssd.logs history
- History of LMON, LMSn, LMD0
- OSWatcher logs
- Operating system logs (/var/log/messages)
To explain the subject a little more, when a communication error occurs between the Nodes due to the network or when the Node to be subjected to the inviction process cannot write heartbeat information on the CFVRR, the Cluster on the node performs the eviction process mentioned above in order to prevent possible data corruption. IMR is responsible for the automation of all these processes.
Instance Membership Recovery (IMR) is responsible for the organization of all cluster members and is also part of the Cluster Group Services structure.
As we mentioned at first, this process results with the restart of the node where the problem is perceived.
Hope to see you again,