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library cache: mutex X

Short Description

A library cache operation is being performed and Oracle is trying to get the library cache mutex in eXclusive mode.

Detailed Description​

Mutexes are a lightweight method of serialising access to an object - in this case the library cache, ensuring that only one operation can take place at any one time.

How to reduce this wait​

  • Pinning hot PL/SQL with dbms_shared_pool.markhot.
  • Increase shared pool size.
  • Setting cursor_sharing to exact or force.

Oracle documentation - DBMS_SHARED_POOL

Julian Dontcheff's blog - Reducing “library cache: mutex X” concurrency with dbms_shared_pool.markhot

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