Change history event monitoring

The change history event monitor captures information about events on the database server that might impact the running of your regular database workload. You can use the data captured by this event monitor to understand changes in the behavior, performance, or stability of your databases and database management system.

When your regular workload experiences a degradation in performance or unexpected behavior is observed, you can correlate the change in workload behavior with events captured by the change history event monitor. The following changes can have a negative impact on your database system.
  • The unexpected creation or dropping of an index
  • The failure of scheduled maintenance to run
  • The changing of a database configuration parameter or database registry variable
Changes can be explicitly caused by a user. For example, an administrator might run a DDL statement that drops an index. Or, changes might occur implicitly or automatically without any user interaction. For example, the self-tuning memory manager (STMM) might change a configuration parameter, or automatic table reorganization might reorganize a table.

Manually tracking changes to the database server can be a difficult task. Historically, the information for different types of changes has been captured through different interfaces. For example, configuration updates are written to the diagnostic log files (for example, the db2diag log files), while utility progress is captured in the database history file. The change history event monitor provides you with a single interface that captures the events that change the behavior and performance characteristics of your database system. Using the event monitor tables, you can investigate any change events that are of interest.

The change history event monitor can capture change-related events for a number of actions and operations, including:
  • Database and database manager configuration parameter changes
  • Registry variable changes
  • Execution of DDL statements
  • Change history event monitor startup
  • Execution of the following database utilities and commands:
    • LOAD
    • ADMIN_MOVE_TABLE procedure invocations
    • BACKUP DATABASE (ONLINE option only)
    • RESTORE DATABASE (ONLINE option only)
    • REORG
Generally, information related to events that occur while the change history event monitor is inactive or the database is offline are not captured. However, the change history event monitor can be configured to capture the registry variable values that are in effect when the an event monitor is activated. Similarly, database and database manager configuration parameter values can be captured when a change history event monitor is activated. When capturing configuration parameter values, the event monitor can detect if any configuration parameters were changed while the event monitor was inactive, and so the event monitor captures configuration parameter values only if changes occur.