Latch Locks

Latch locks are lightweight synchronization mechanisms used by Oracle to protect shared data structures in memory. Here are some common latch locks and their causes:

1. cache buffers chains latch: This latch protects the buffer cache chains, which are used to manage the buffer cache. Contention on this latch can occur due to:
   • High buffer cache activity (for example, frequent reads and writes).
   • Poor buffer cache sizing or configuration.
   • High concurrency (for example, many sessions accessing the same data).
2. cache buffers lru chain latch: This latch protects the LRU (Least Recently Used) chain, which is used to manage the buffer cache. Contention on this latch can occur due to:
   • High buffer cache activity (for example, frequent reads and writes).
   • Poor buffer cache sizing or configuration.
3. redo allocation latch: This latch is used to allocate space in the redo log buffer. Contention on this latch can occur due to:
   • High redo log activity (for example, frequent commits or high DML activity).
   • Poor redo log buffer sizing or configuration.
4. redo copy latch: This latch is used to copy redo log data from the log buffer to the redo log files. Contention on this latch can occur due to:
   • High redo log activity (for example, frequent commits or high DML activity).
   • Poor redo log buffer sizing or configuration.
5. library cache latch: This latch protects the library cache, which is used to store parsed SQL statements and other metadata. Contention on this latch can occur due to:
   • High SQL parsing activity (for example, frequent execution of dynamic SQL).
   • Poor cursor management (for example, not using bind variables).
6. shared pool latch: This latch protects the shared pool, which is used to store shared SQL and PL/SQL objects. Contention on this latch can occur due to:
   • High shared pool activity (for example, frequent parsing or loading of SQL and PL/SQL objects).
   • Poor shared pool sizing or configuration.