In this article we are going to see Oracle Manageability Monitor Lite Process (MMNL) Background Process.
- Performs tasks relating to manageability, including active session history sampling and metrics computation
- Manageability Monitor Process (MMON) and Manageability Monitor Lite Process (MMNL) are background processes that perform tasks related to the Automatic Workload Repository (AWR). The AWR is a repository of historical performance data that includes cumulative statistics for the system, sessions, individual SQL statements, segments, and services. It is used for problem detection and self-tuning purposes.
- MMNL gathers session statistics (such as the user ID, state, the machine, and the SQL it is executing) and stores them in the Active Session History (ASH) buffer. Specifically, MMNL samples the V$SESSION and V$SESSION_WAIT views every second in the SGA and then records that data in the V$ACTIVE_SESSION_HISTORY view. Inactive sessions are not sampled. The ASH is designed as a rolling buffer in memory, and therefore, earlier information is overwritten when needed. When the ASH buffer becomes full or when MMON takes a snapshot, MMNL flushes (empties) the ASH buffer into the DBA_HIST_ACTIVE_SESS_HISTORY view in the AWR. Because space is expensive, only one in every 10 entries is flushed. MMNL also computes metrics.
- This process will flush the ASH buffer to AWR tables when the buffer is full or a snapshot is taken.
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