The purpose of IPL initially is to load the operating system from auxiliary storage (disk) into memory and begin executing it. If you are a PC oriented person this would be analogous to Booting up a PC.

Now if the system is already running an IPL can do a certain amount of cleanup.

In my opinion there are a limited number of reasons for an IPL, these are:

1) Any maintenance that requires the system be shut down. Pretty obvious one.. :-)
2) PTF application that requires an IPL
3) If Percentage of Temporary Addresses Used has surpassed 90%. (It won't even reset below 85%).
4) If the amount of Auxiliary Storage used by Unprotected Storage is significant enough to warrant cleanup.

Back in the early "AS/400 Days" there were many additional cleanup steps that happened only during IPL. These steps are now part of CHGCLNUP and run nightly unless you've disabled them. These include spooled file space cleanup, history log cleanup, joblog cleanup, and message queue cleanup.

Describing all of what happens in an IPL is beyond this list but you can see a list of what some of the items are here:

- Larry "DrFranken" Bolhuis

On 10/13/2012 10:54 AM, John Mathew wrote:
what is the purpose of IPL(Intial Program Load). What are steps involved in IPL.
thanks in advance.

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