Oracle Metric log file sync


This post is mainly to make other people aware that on a RAC system there is a relationship between high inter-node block sharing traffic (Global Cache) and “log file sync”, and that the log file sync events are a direct side effect of the high inter-node block sharing that is occurring.

This occurs when a user commits a transaction (a transaction is not considered committed until all of the redo to recover the transaction has been successfully written to disk).

In single instance database  when we issue commit it just write log buffer into redo log file but in RAC database there is little more to it, it will perform the same operation and broadcast this commit info to other remote LMS and waits for acknowledgement from them. once it gets acknowledgement from remote lms only then commit gets completed.Untitled

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