mon_heap_sz - Database system monitor heap size configuration parameter

This parameter determines the amount of the memory, in pages, to allocate for database system monitor data. Memory is allocated from the monitor heap when database monitoring activities are performed. Monitoring activities include turning on monitor switches, resetting monitor data, activating an event monitor or sending monitor events to an active event monitor.
With Version 9.5, this database configuration parameter has a default value of AUTOMATIC, meaning that the monitor heap can increase as needed until the instance_memory limit is reached.
Configuration type
Database manager
Applies to
  • Database server with local and remote clients
  • Database server with local clients
  • Partitioned database server with local and remote clients
Parameter type
Configurable online
Default [range]
32-bit platforms
Automatic [0 - 60 000]
64-bit platforms
Automatic [0 - 2 147 483 647]
Unit of measure
Pages (4 KB)
When allocated
When the database manager is started with the db2start command
When freed
When the database manager is stopped with the db2stop command

A value of zero prevents the database manager from collecting database system monitor data.

Recommendation: The amount of memory required for monitoring activity depends on the number of monitoring applications (applications taking snapshots or event monitors), which switches are set, and the level of database activity.

If the configured memory in this heap runs out and no more unreserved memory is available in the instance shared memory region, one of the following events will occur:

  • When the first application connects to the database for which this event monitor is defined, an error message is written to the administration notification log.
  • If an event monitor being started dynamically using the SET EVENT MONITOR statement fails, an error code is returned to your application.
  • If a monitor command or API subroutine fails, an error code is returned to your application.
  • If an application needs to send an event monitor record but cannot allocate the record out of monitor heap, the application might be blocked until a record is allocated.