Estimating the storage needed for locks

You can estimate the amount of storage needed for locks.

About this task

An estimate of the amount of storage needed for locks is calculated when DB2® is installed. The CLIST stores the greater of 2GB or the calculated value of the NUMLKUS subsystem parameter.

Procedure

To estimate the storage that is required for DB2 locks:

  1. Gather the following information:
    • The maximum number of row or page locks per user, in the value of the NUMLKUS subsystem parameter.
    • The maximum number of allied threads that can be active concurrently, in the value of the CTHREAD subsystem parameter.
    • The maximum number of database access threads that can be active concurrently, in the value of the MAXDBAT subsystem parameter.
  2. Use the following formula, which assumes that each lock needs 540 bytes of storage: 
    Bytes of Storage = 100MB + 
 (CTHREAD + MAXDBAT)
 
×
 NUMLKUS
 
×
 540 bytes)
    The result is a high-end estimate of the storage space that is needed for locks, because the formula assumes that the maximum number of users are connected, and each user holds the maximum number of locks.