rstrt_light_mem - Restart light memory configuration parameter

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

Default [range]

AUTOMATIC [1 - 10 for AUTOMATIC; the user-defined range is 1 - 50]

Units of measure

Percentage of instance memory

When allocated

When the instance is started

When freed

When the instance is stopped

Having rstrt_light_mem set to AUTOMATIC means that when the instance is started, the DB2® database manager automatically calculates a fixed upper bound for the amount of memory to be pre-allocated and reserved for restart light recovery purposes. The specified amount of memory is reserved to accommodate failed members that need to be restarted on a host other than their home host (restart light mode). The DB2 database manager calculates the appropriate value based on the current setting for instance_memory and numdb (maximum number of currently active databases) as well as the number of members on the host . The automatically calculated value ranges between 1 and 10 percent of the instance memory limit and is included in the total amount of instance memory. Users can also explicitly set rstrt_light_mem to a value between 1 and 50 percent of the instance memory limit. Additional memory could result in an improvement in the recovery time, especially when there are multiple databases that need to be recovered. The additional memory will also result in less memory being available for normal work, reducing the throughput the members can handle.

The parameter is configurable but not online. Once the reserved recovery memory has been allocated when the DB2 instance is started, the amount of memory is fixed and will not change unless the configuration value is changed and the DB2 instance is globally stopped and started again.

To display information about the total amount of memory allocated on a host, use db2pd with the new -totalmem option. This information will also include the amount of restart light memory allocated on a host. Only information about the current host being accessed is returned, but db2pd can be run on separate hosts in parallel.

The rstrt_light_mem is only applicable to SD mode and does not display in ESE mode.