The Page Frame Structure

Occasionally we need to enquire into the ownership and disposition of real storage. The PF is used to track the use of all frames of real storage, whether allocated, idle (pending freeing) or free.

The PF is formatted using the .MP KDB and DF command. .MP will optionally take the frame number (real address MOD 4K) as a parameter.

# .mp
ffe1b000 InUse: pVP=ff406000 RefCnt=0001 Flg=0 ll=00 sl=00 Blk=00000 Frame=00000
ffe1b00c InUse: pVP=ff406050 RefCnt=0001 Flg=0 ll=00 sl=00 Blk=00000 Frame=00001
ffe1b018 InUse: pVP=ff40605a RefCnt=0001 Flg=0 ll=00 sl=00 Blk=00000 Frame=00002
ffe1b024 InUse: pVP=ff406064 RefCnt=0002 Flg=0 ll=00 sl=00 Blk=00000 Frame=00003
ffe1b030 InUse: pVP=ff40606e RefCnt=0001 Flg=0 ll=00 sl=00 Blk=00000 Frame=00004

Of particular interest are:

Frame=fffff

The real storage frame number represented by this PF.
pVP
The address of the related Virtual Page Structure (non-free PFs only). See next section.
ll
The long term lock count.

This is non-zero when an otherwise non-resident page is long-term locked, that is prohibited from being discarded or swapped, and expected to be so for a relatively long time.

sl
The short term lock count.

This is non-zero when an otherwise non-resident page is short-term locked, that is prohibited from being discarded or swapped, but temporarily so (much less than 10 seconds).

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