Long IPL Times in SRCD6000298 Due to Saves

When an Integrated File System (IFS) object or any type of object (database object, program object, etc.) is touched for the first time during the IPL, the first page of the object is updated. Object checking is a part of the IBM i operating system architecture and performed on all objects. As an example, when a save of the entire IFS is performed, every IFS object is touched; thus the first page of every IFS object is changed by the object checking process.

Save operations create changed pages in memory. If an IPL is performed immediately after a save operation, the result will be extended time during power down, dependent upon the number of changed pages in memory. This can be most noticeable during power down at System Reference Code (SRC) D6000298 (SRCD6000298). This SRC represents storage management shutdown processing, in which pages residing in main storage are forced out to DASD.

Ideally for power down performance, you should avoid an IPL immediately after a save of the IFS. If that is not possible, the CLRPOOL command should be considered prior to the IPL. This command forces all of the changed pages out to DASD faster than standard power down procedures and can be done at the convenience of the user. In cases where the IPL is performed immediately after the save and the CLRPOOL command was not issued, the user may still restore their saves after the IPL and the time involved depends upon the changed pages in memory being forced to DASD. On systems with large amounts of memory and low activity, changed pages may remain in memory for extensive amounts of time.

The following related PTFs are explained in APAR MA35264 and may also reduce power down times:
R540 MF42486
R545 MF42491