topic Re: calculating sysdump.dmp size in Operating System - OpenVMS

calculating sysdump.dmp size

Steven_101 — Wed, 07 Jan 2009 20:38:22 GMT

Trying to create a generic script to deploy to all my servers to gather infomation on sysdump.dmp and see it is the righr size

Found the following

On Alpha systems, use the following formula:
size-in-blocks(SYS$SYSTEM:SYSDUMP.DMP)
= size-in-pages(physical-memory) * blocks-per-page
+ number-of-error-log-buffers * blocks-per-buffer
+ 10
where:
size-in-pages
Is the size of physical memory, in pages. Use the DCL command SHOW MEMORY to determine the total size of physical memory on your system.

blocks-per-page
Is the number of blocks per page of memory.

On Alpha systems, calculate the number of blocks per page of memory by dividing the system's page size by 512 (the size of a block). Use the following commands:
$ PAGESIZE==F$GETSYI ("PAGE_SIZE")
$ BLOCKSPERPAGE=PAGESIZE/512
$ SHOW SYMBOL BLOCKSPERPAGE

number-of-error-log-buffers
Is the value of the system parameter ERRORLOGBUFFERS.

blocks-per-buffer
Is the value of the system parameter ERLBUFFERPAGES.

when I tried to use it the answer comes out over twice the size of what agent$params.report says the dump file size should be

@dsize
$!
$ memsize= f$getsyi("memsize")
$ PAGESIZE =F$GETSYI ("PAGE_SIZE")
$ BPP =PAGESIZE/512
$ eb = f$getsyi("ERRORLOGBUFFERS")
$ bpb = f$getsyi("ERLBUFFERPAGES")
$ dsize = memsize*bpp+eb*bpb+10
$ sho sym memsize
MEMSIZE = 524288 Hex = 00080000 Octal = 00002000000
$ sho sym pagesize
PAGESIZE = 8192 Hex = 00002000 Octal = 00000020000
$ SHOW SYMBOL BPP
BPP = 16 Hex = 00000010 Octal = 00000000020
$ sho sym eb
EB = 4 Hex = 00000004 Octal = 00000000004
$ sho sym bpb
BPB = 8 Hex = 00000008 Octal = 00000000010
$ sho sym dsize
DSIZE = 8388650 Hex = 0080002A Octal = 00040000052
$!

sear sys$system:agen$params.report dump
Dump file calculations:
A 4168027 block dump file should be created.

Re: calculating sysdump.dmp size

Andy Bustamante — Wed, 07 Jan 2009 21:05:02 GMT

The calculation you have is for a full uncompressed dumpfile. The value of the system parameter dumpstyle can modify file requirements. See chapter 2 of the OpenVMS System Analysis Tools Manual at http://h71000.www7.hp.com/doc/82final/6549/6549pro.html. The default value (dumpstyle=9) is for a compressed selective dump on systems with greater than 128 mb of memory.

Autogen will take this into account. You may want to bump the autogen value by 10 percent so so, disk space is inexpensive and on the very rare instances of a system crash, you really want the crash dump to complete.

Andy Bustamante

Re: calculating sysdump.dmp size

Jess Goodman — Wed, 07 Jan 2009 21:07:14 GMT

What is SYSGEN parameter DUMPSTYLE set to? If it is set for compressed dumps AUTOGEN will take that into account.

In current versions of VMS (since V7.2 ?) the error log is dumped to a separate file, SYS$ERRLOG.DMP.

Re: calculating sysdump.dmp size

John Gillings — Wed, 07 Jan 2009 23:26:38 GMT

Steven,

Why would you want to reinvent a perfectly good wheel?

Set DUMPFILE=0 in MODPARAMS.DAT to prevent automatic changes in dump file size. Now execute

$ @SYS$UPDATE:AUTOGEN GETDATA GENPARAMS

This is a minimal impact AUTOGEN. Since it skips SAVPARAMS, it doesn't record any information about the system, and it doesn't get to SETPARAMS, so no changes are made.

AUTOGEN will calculate the recommended size of dump file, based on lots of things, including compression settings. You can then manually set the file size using SYSGEN, or setting DUMPFILE in MODPARAMS.DAT.

Re: calculating sysdump.dmp size

Steven_101 — Thu, 08 Jan 2009 00:00:40 GMT

I realized on the way home that dumpstyle might be taken in the calculation. Somtimes you just need to walk-away for awhile and the answer comes to you

thanks guys

Re: calculating sysdump.dmp size

Steven_101 — Thu, 08 Jan 2009 13:57:26 GMT

well now its really interseting. Servers are physically identical AlphaServer ES47 7/1150
server #1
BE3VAX>>mcr sysgen sho dump
Parameter Name Current Default Min. Max. Unit Dynamic
-------------- ------- ------- ------- ------- ---- -------
DUMPSTYLE 9 9 0 -1 Bitmask D
DUMPBUG 1 1 0 1 Boolean
BE3VAX>>sho mem/phy
System Memory Resources on 8-JAN-2009 08:37:26.56

Physical Memory Usage (pages): Total Free In Use Modified
Main Memory (8.00GB) 1048576 411627 630082 6867

Of the physical pages in use, 19369 pages are permanently allocated to OpenVMS.
BE3VAX>>sear sys$system:agen$params.report dump
Calculations for page, swap, and dump files.
Errorlog dumpfile calculations:
No errorlog dump file modifications should be made.
Errorlog dumpfile will remain at 778 blocks.
Dump file calculations:
No dump file modifications should be made.
Dumpfile on device DSA194: will remain at 17825792 blocks.

server #2
DEV1AX>>mcr sysgen sho dump
Parameter Name Current Default Min. Max. Unit Dynamic
-------------- ------- ------- ------- ------- ---- -------
DUMPSTYLE 9 9 0 -1 Bitmask D
DUMPBUG 1 1 0 1 Boolean
DEV1AX>>sho mem/phy
System Memory Resources on 8-JAN-2009 08:35:54.01

Physical Memory Usage (pages): Total Free In Use Modified
Main Memory (8.00GB) 1048576 413135 627718 7723

Of the physical pages in use, 17488 pages are permanently allocated to OpenVMS.
DEV1AX>>sear sys$system:agen$params.report dump
Calculations for page, swap, and dump files.
Errorlog dumpfile calculations:
No errorlog dump file modifications should be made.
Errorlog dumpfile will remain at 778 blocks.
Dump file calculations:
A 1439644 block dump file should be created.

Re: calculating sysdump.dmp size

John Gillings — Fri, 09 Jan 2009 00:11:11 GMT

Steven,

What is DUMPFILE set to in MODPARAMS? It will override AUTOGEN calculations. It's probably 0 in both cases, but the first node has a dump file, while the second does not. Try RENAMEing the dump file on the first node and check the AUTOGEN result.

I'd also be reading the complete text of the autogen "Dump file calculations" section, rather than just the lines containing the word "dump".

If you really want to know how AUTOGEN calculates the size, why not read the code? You may even be able to find a pre DCLDIET copy of AUTOGEN.COM on the web somewhere which may be a bit more readable.

On the other hand, you could just trust that the folks who wrote AUTOGEN know what they're doing and not spend your time re-inventinting it.

Re: calculating sysdump.dmp size

Steven_101 — Fri, 09 Jan 2009 01:43:43 GMT

The value of dumpfile=0 only controls whether or not autogen will attempt to create a new dumpfile.

Both systems have dumpfiles on them. The troubling questions is why 2 physically similar systems want to calculate the size of the sysdump.dmp differently.

Granted 1 server has dumpfile set to 0, and the other has no entry in modparams.dat

********************************************
DEV1AX>>sear sys$system:modparams.dat;* dump
%SEARCH-I-NOMATCHES, no strings matched
DEV1AX>>dir/date/siz=all sys$system:sysdump.dmp

Directory SYS$SYSROOT:[SYSEXE]

SYSDUMP.DMP;3 2030193/2030364 20-OCT-2007 15:45:46.24

Total of 1 file, 2030193/2030364 blocks.
DEV1AX>>sho mem/phy
System Memory Resources on 8-JAN-2009 20:37:15.67

Physical Memory Usage (pages): Total Free In Use Modified
Main Memory (8.00GB) 1048576 411306 629227 8043

Of the physical pages in use, 17488 pages are permanently allocated to OpenVMS.
DEV1AX>>mcr sysgen sho dump
Parameter Name Current Default Min. Max. Unit Dynamic
-------------- ------- ------- ------- ------- ---- -------
DUMPSTYLE 9 9 0 -1 Bitmask D
DUMPBUG 1 1 0 1 Boolean
DEV1AX>>dir/date sys$system:agen$params.report;

Directory SYS$SYSROOT:[SYSEXE]

AGEN$PARAMS.REPORT;15
5-DEC-2008 19:50:49.50

Total of 1 file.
DEV1AX>>sear sys$system:agen$params.report; dump
Calculations for page, swap, and dump files.
Errorlog dumpfile calculations:
No errorlog dump file modifications should be made.
Errorlog dumpfile will remain at 778 blocks.
Dump file calculations:
A 1439644 block dump file should be created.
DEV1AX>>
*******************************************

BE3VAX>>sear modparams.dat dump
DUMPFILE = 0
BE3VAX>>dir/date/siz=all sysdump.dmp

Directory SYS$SYSROOT:[SYSEXE]

SYSDUMP.DMP;1 *******/******* 24-MAR-2008 23:48:45.95

Total of 1 file, 17825792/17825808 blocks.
BE3VAX>>sho mem/phy
System Memory Resources on 8-JAN-2009 20:40:54.90

Physical Memory Usage (pages): Total Free In Use Modified
Main Memory (8.00GB) 1048576 412623 628685 7268

Of the physical pages in use, 19369 pages are permanently allocated to OpenVMS.
BE3VAX>>dir/date agen$params.report;

Directory SYS$SYSROOT:[SYSEXE]

AGEN$PARAMS.REPORT;118
3-JAN-2009 04:00:00.27

Total of 1 file.
BE3VAX>>sear AGEN$PARAMS.REPORT dump
Calculations for page, swap, and dump files.
Errorlog dumpfile calculations:
No errorlog dump file modifications should be made.
Errorlog dumpfile will remain at 778 blocks.
Dump file calculations:
No dump file modifications should be made.
Dumpfile on device DSA194: will remain at 17825792 blocks.
BE3VAX>>

Re: calculating sysdump.dmp size

John Gillings — Fri, 09 Jan 2009 05:58:18 GMT

>The troubling questions is why 2
>physically similar systems want to
>calculate the size of the sysdump.dmp
>differently.
>
>Granted 1 server has dumpfile set to 0,
>and the other has no entry in modparams.dat

Different configurations, different results.

Try comparing apples with apples. Set DUMPFILE=0 on both systems, or remove it from both systems. For a clean slate experiment, remove the DUMPFILE setting and RENAME the dump files. As long as you don't execute the GENFILES phase you won't affect existing files.

AUTOGEN is deliberately conservative. It won't go changing things unless it's told it can, and the difference is significant enough (definition varies, see source).

There are also other variables which affect the size which may be different between your two systems. For exaple, a quick look at AUTOGEN.COM suggests GBLPAGES, BALSETCNT and WSSIZEs of various processes enter into the calculation.

Bottom line is, the systems are sufficiently different that you get different results from AUTOGEN. If you're confident that the values defined in MODPARAMS are correct for the workloads why would it matter that the resulting dump files sizes are different? If you want them the same, choose the value that you like best and set it in MODPARAMS.

Consider the real cost of the disk space consumed by the dump file. Is it worth worrying about?

Re: calculating sysdump.dmp size

Paul Jerrom — Mon, 12 Jan 2009 02:13:05 GMT

>>The value of dumpfile=0 only controls whether or not autogen will attempt to create a new dumpfile.

No, dumpfile=0 tells autogen not to change the dumpfile size, ie use the dumpfile.dmp that is already there.