Active Session History (ASH) Reports

ASH is Helpful to identify performance issues in old sessions. ASH Collects samples of active sessions every second (waiting for non-idle events, or on the CPU working) from v$sessions (inactive sessions are not captured). Sampled data collected to circular buffer in SGA and the same can be accessed through v$views. V$ACTIVE_SESSION_HISTORY view provides the sampled session activity for the instance. Using the Active Session History you can examine and perform the detailed analysis on the current data in the v$ACTIVE_SESSION_HISTORY and the past data in the DBA_HIST_ACTIVE_SESS_HISTORY view. ASH report is a small report compared to the AWR report which will provide the db/instance details for a short period of time. ASH Report Covers a much shorter period of time (e.g 5 min) compared to an AWR Report (e.g 30 min or 1 hour) . ASH Report captures the following things : • SQL Identifier of SQL Statement. • Object Number, File number and block number • Wait event identifier and session serial number • Module and Action name. • Client identifier of the session • Service hash identifier Major ASH Report sections are : Top User events Top Background Events. Top Cluster Events. Top Service/Module Top Sql Command Types Top Phases Of Execution Top Remote Instances Top SQl With Top Events.