Manageability Monitor Processes (MMON and MMNL)
The manageability monitor process (MMON) performs many tasks related to the Automatic Workload Repository (AWR). For example, MMON writes when a metric violates its threshold value, taking snapshots, and capturing statistics value for recently modified SQL objects.
The manageability monitor lite process (MMNL) writes statistics from the Active Session History (ASH) buffer in the SGA to disk. MMNL writes to disk when the ASH buffer is full.
https://docs.oracle.com/cd/E11882_01/server.112/e40540/cncptdba.htm#CNCPT860
Automatic Workload Repository (AWR)
Automatic Workload Repository (AWR) is a repository of historical performance data that includes cumulative statistics for the system, sessions, individual SQL statements, segments, and services. These statistics are the foundation of performance tuning. By automating the gathering of database statistics for problem detection and tuning, AWR serves as the foundation for database self-management.
As shown in Figure 18-8, the database stores recent AWR statistics in the SGA. By default, the MMON process gathers statistics every hour and creates an AWR snapshot (see "Manageability Monitor Processes (MMON and MMNL)"). A snapshot is a set of performance statistics captured at a specific time. The database writes snapshots to the SYSAUX tablespace. AWR manages snapshot space, purging older snapshots according to a configurable snapshot retention policy.
Automatic Workload Repository (AWR)
Automatic Workload Repository (AWR) is a repository of historical performance data that includes cumulative statistics for the system, sessions, individual SQL statements, segments, and services. These statistics are the foundation of performance tuning. By automating the gathering of database statistics for problem detection and tuning, AWR serves as the foundation for database self-management.
As shown in Figure 18-8, the database stores recent AWR statistics in the SGA. By default, the MMON process gathers statistics every hour and creates an AWR snapshot (see "Manageability Monitor Processes (MMON and MMNL)"). A snapshot is a set of performance statistics captured at a specific time. The database writes snapshots to the SYSAUX tablespace. AWR manages snapshot space, purging older snapshots according to a configurable snapshot retention policy.
