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Operating System - OpenVMS
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Non Paged Dynamic Memory

Wim Van den Wyngaert
Honored Contributor

Non Paged Dynamic Memory

I have a VMS 7.3 system on which I found that
the largest free block is 0. But I don't find this info when doing /full. Why ?

ARBZY/MGRWVW>sh mem/pool

Dynamic Memory Usage: Total Free In Use Largest
Nonpaged Dynamic Memory (Mb) 6.12 3.61 2.50 0.00

ARBZY/MGRWVW>sh mem/pool/fu
System Memory Resources on 9-JAN-2004 09:15:51.45

Nonpaged Dynamic Memory (Lists + Variable)
Current Size (Mb) 6.12 Current Size (Pagelets) 12544
Initial Size (Mb) 4.60 Initial Size (Pagelets) 9424
Maximum Size (Mb) 26.78 Maximum Size (Pagelets) 54864
Free Space (Mb) 3.61 Space in Use (Mb) 2.50
Largest Var Block (Kb) 4.56 Smallest Var Block (bytes) 64
Number of Free Blocks 7382 Free Blocks LEQU 64 bytes 86
Free Blocks on Lookasides 4141 Lookaside Space (Mb) 1.16
Honored Contributor

Re: Non Paged Dynamic Memory

If you want some details about memory, you shoud do
$ ana/sys
clue memory

you have some qualifiers
clue memory/layout
clue memory/lookaside

And you should check if you have had some pool expansion failures, with
$ mc agen$feedback
(this creates a new file sys$system:agen$feedback.dat)
$ search sys$system:agen$feedback.dat fail

look at the npagedyn_allocafail



Honored Contributor

Re: Non Paged Dynamic Memory

sorry tyhere is a typo, it is
Wim Van den Wyngaert
Honored Contributor

Re: Non Paged Dynamic Memory


Thanks. I made a mistake. I didn't convert the units. 4.56 KB is 0.00 MB.
Ian Miller.
Honored Contributor

Re: Non Paged Dynamic Memory


Will display the types of structures and what is using them. On my systems its typically LKB lock structures using most due to lots of locks.
Purely Personal Opinion
John Gillings
Honored Contributor

Re: Non Paged Dynamic Memory


I'm sure this is an issue of granularity. The size of the largest free packet is too small to be non-zero when expressed in Mb to 2 decimal places! This is probably nothing to get alarmed about, though it does indicate a fair amount of fragmentation, relative to your free space.

There are lots of ways of looking at PAGEDYN and NPAGEDYN in detail, including SHOW MEMORY and SDA.

On V7.3-2 systems, and V7.3-1 systems with recent ECOs there are (as yet undocumented) items for F$GETSYI which return memory statistics:


and the same with prefix "PAGED_". The units are always bytes regardless of the process UNITS setting.

A crucible of informative mistakes