DKUPDTWT parameter

# seconds after file's last update before file is updated on disk

Summary

Default value

0

Parameter type

System

Where set

On User 0's parameter line or reset by system manager

Related products

All

Introduced

Model 204 V3.2

Description

How long disk buffers, containing a file's modified pages, must have aged (in seconds) before they can be written to disk. Even after the write, the pages remain in the buffer pool for future reference until the file is closed by the last user.

If DKUPDTWT is zero, Model 204 writes all of a file's modified pages to disk at the end of the last in-flight update of the file. The user who completed the last in-flight update waits for this disk update process to complete and for the message stating that the disk update is complete.

If DKUPDTWT is nonzero, Model 204 delays the start of the disk update process for at least DKUPDTWT seconds, after which it can be the checkpoint pseudo subtask (CHKPST) that performs the disk update. The user who completed the last in-flight update does not have to wait for the disk update process to complete.

If DKUPDTWT is nonzero, the CHKPST and CHKPTIMR pseudo subtasks are started automatically at Model 204 initialization. An error message informs you if the NSUBTKS parameter is set too low to start these pseudo subtasks.

DKUPDTWT has a maximum of 60, and it also depends on the CPTIME parameter setting. If CPTIME is nonzero, DKUPDTWT must be less than or equal to CPTIME*30.

The system manager can reset DKUPDTWT to zero while the online is running, and to a nonzero value as long as the CHKPST and CHKPTIMR pseudo subtasks were started during Model 204 initialization.

If sub-transaction checkpointing is activated by setting CPTYPE to 1, then DKUPDTWT must be set to 0