Overview
Active Session History (ASH) is a diagnostic tool that records information about all active sessions in the database. OceanBase ASH reports analyze instantaneous exceptions and provide more fine-grained diagnostic information than performance reports. General performance reports provide snapshot information at the hourly level. Their information granularity is not at the session level. Therefore, these performance reports can hardly provide execution details for some instantaneous jitters. However, we can solve such problems by using fine-grained diagnostic information at the session level in ASH reports.
Application scenarios
ASH reports are used to diagnose the following types of exceptions and issues that occur transiently:
- Transient performance issues that occur for several minutes.
- Performance issues in various dimensions, such as time, sessions, modules, operations, or SQL statements.
ASH reports provide you with the information about SQL statements that use the most database resources during a diagnosis period, the execution details of historical sessions of an OceanBase cluster, and other information. You can optimize the SQL statements based on the information and improve the SQL execution efficiency.