746138 - Analyzing lock table overflows

Reason and Prerequisites

The maximum number of locks in the lock table is subject to an upper limit that is set by the profile parameter enque/table_size. The profile parameter enque/table_size determines the size of the lock table in KBs. You can use transaction SM12 -> "Extras" -> "Statistics" to determine both the maximum number and current number of entries.
The lock table may overflow if:

• the lock table configuration is too small

• an application sets lots of locks

• the update hangs and, as a result, numerous locks inherited by the update task exist

Up to now, subsequent analysis could not be performed to determine which lock types and which lock owners mainly contributed to the lock table overflow.

Solution

The kernel patch described here saves information about the cause of a lock table overflow. This information can be read retrospectively.
The kernel patch concerns kernel releases 4.6D, 6.40 and higher.

The following information is saved for the last ten lock table overflows:

• the three lock owners with the most locks

• the three lock arguments with the most locks

Use transaction SM12 to obtain the raw information and particular selection data:

• Table:       "#01_002"

• Argument:      "#01_002"

• Client:       "#01"

• User name:  "#01_002"

In addition, this information is stored in the file ENQHISOVR in DIR_HOME on the enqueue server.

The overflow information is written as of the following kernel patch levels:

4.6D:  1856
6.40:    21

For all higher releases, the overflow information is written as of patch level 0.