Saturday, March 28, 2020

ORA-00972: identifier is too long


In Oracle, the maximum length for the name of an object (Table, View, Procedure, Package, Function, Materialized View etc.) is 30 characters. Likewise, the name of a column of a table or view should also not exceed 30 characters. In the following I am providing a few examples where we will see ORA-00972 error.

Friday, March 20, 2020

SQL Plan Management and SQL Baseline

Before you read this article, I would suggest you to read my articles about bind variable peeking and adaptive cursor sharing.
Starting 11g release, adaptive cursor sharing makes optimizer to generate and select multiple execution plans based on the bind variable values passed during the execution. Oracle also introduced SQL Plan Management feature starting 11g whereby the history of plans of an SQL is maintained in SQL Baseline and out of which one or more plans can become “accepted” and can be used for that SQL. This is our choice to make plan(s) “accepted” if think that plan is optimal. We may ignore sub-optimal plans. In this will explain SQL Plan Management using an example.

Friday, March 6, 2020

gc buffer busy acquire and gc buffer busy release


These two wait events are similar to ”buffer busy wait” that you might have observed which is recorded when a session tries to access a data block/buffer which is already being accessed by another session that is connected to the same instance and buffer is also in the current instance’s buffer cache. In RAC environment, if a session tries to read a buffer from a remote instance’s buffer cache but the buffer is already being read by a different session, a “gc buffer busy acquire” wait event is recorded. If a session tries to read a buffer from the buffer cache of local instance, but buffer is already being read into remote instance’s buffer cache from local cache by a session connected to that remote instance, a “gc buffer busy release” wait event is recorded.  

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