Max storage for locks setting when upgrading to DB2 v8

Donna Domovic

Max storage for locks setting when upgrading to DB2 v8
Hello,

We're in the process of upgrading from DB2 v7 to DB2 v8 and I'm trying to
figure out how to best estimate the value for the MLMT IRLM parameter (max
storage for locks). I issued the modify command to display the current IRLM
stats command for 2 of our systems with the following results but I don't know
what to do from here to translate that in to the MLMT parameter value. I'd
like to have an idea of if the default value of 2 will be large enough to handle
our locks.

F DB2TIRLM,STATUS,STOR
DXR100I DJ2T001 STOR STATS 627
PC: NO MAXCSA: 15M LTE: 4M RLE: 38552 RLEUSE: 1310
CSA USE: ACNT: 4612K AHWM: 6404K CUR: 6470K HWM: 8254K
ABOVE 16M: 114 6470K BELOW 16M: 0 0K
CLASS TYPE SEGS MEM TYPE SEGS MEM TYPE SEGS MEM
ACCNT T-1 64 4096K T-2 8 512K T-3 1 4K
PROC WRK 7 42K SRB 2 2K OTH 2 2K
MISC VAR 29 1913K N-V 6 22K FIX 1 24K
DXR100I End of display


F DB3PIRLM,STATUS,STOR
DXR100I DJ3P003 STOR STATS 262
PC: NO MAXCSA: 15M LTE: 16M RLE: 143360 RLEUSE: 3268
CSA USE: ACNT: 8520K AHWM: 8520K CUR: 10M HWM: 12M
ABOVE 16M: 225 10M BELOW 16M: 0 0K
CLASS TYPE SEGS MEM TYPE SEGS MEM TYPE SEGS MEM
ACCNT T-1 120 7680K T-2 13 832K T-3 2 8K
PROC WRK 11 66K SRB 33 33K OTH 15 15K
MISC VAR 30 3833K N-V 92 108K FIX 2 36K
DXR100I End of display

Thanks,
Donna Domovic

______________________________________________________________________

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Roger Miller

Re: Max storage for locks setting when upgrading to DB2 v8
(in response to Donna Domovic)
2 gigabytes is more than you've had before. IRLM and DB2 can manage with
applications that are not well behaved, but you do need the real memory, if
applications are behaving very badly. If you do have the memory, then 3
would be adding 50% to what you had with PC=YES before. If you had
PC=NO, then this provides a lot more than the prior MAXCSA.

Here are some pastes from my Information Center update.

MAX STORAGE FOR LOCKS Acceptable values: 2 to 100
Default: 2
Update: edit IRLM start procedure
Specify, in gigabytes, the maximum amount of private storage available
above the 2–GB bar that the IRLM for this DB2 uses for its lock control block
structure. This value becomes the setting of the MLMT parameter for the IRLM
address space procedure. The IRLM address |space procedure sets the z/OS
MEMLIMIT value for the address space.

Ensure that you set this value high enough so that IRLM does not reach the
limit. The value that you choose should provide space for possible retained
locks. IRLM only gets storage as it needs it, so choose a large value. You can
also change the value dynamically by using the z/OS command MODIFY
irlmproc,SET,MLT. See IRLM address space (IRLMPROC) and Common service
area for more information about how IRLM uses storage. For data sharing
settings, see DB2 Data Sharing: Planning and Administration.|

You can estimate the IRLM control block structure at 540 bytes per lock. IRLM
no longer supports placing locks in ECSA. All IRLM locks are now placed in the
IRLM private address space above the bar.

The PC and MAXCSA parameters are no longer used, but you must maintain
them for compatibility reasons. You must specify the parameters and values,
but their values are not used. The MAXCSA value must be in the range 0-
9999. The amount of available storage for IRLM private control blocks,
including locks, is determined by the operating system and site-specific IPL
parameters. IRLM reserves approximately 10% of the available private storage
to be used for must-complete lock requests.

Use the MODIFY irlmproc,STATUS,STOR command to view and monitor the
amount of private storage that IRLM has available. You can adjust the amount
of below the bar private storage dynamically with the MODIFY irlmproc
SET,PVT command. You can adjust the limit for above the bar private storage
dynamically with the MODIFY irlmproc SET,MLT command. The new value
remains in effect until the next time IRLM is stopped and restarted or until the
MODIFY command is issued successfully again. For below the bar private
storage, this only changes the monitoring threshold of private storage for
IRLM. For above the bar private storage, this only updates the MEMLIMIT that
z/OS uses to control the amount of above the bar storage that can be
requested by an address space. Neither command changes the physical
amount that the operating system assigned to the address space.

Enabling data sharing further increases the storage that IRLM requires.
Sysplex query parallelism requires additional storage beyond what is required
for data sharing.

Roger Miller, DB2 for z/OS


On Fri, 12 Dec 2008 17:52:23 +0000, Donna Domovic
<[login to unmask email]> wrote:

>Hello,
>
>We're in the process of upgrading from DB2 v7 to DB2 v8 and I'm trying to
>figure out how to best estimate the value for the MLMT IRLM parameter (max
>storage for locks). I issued the modify command to display the current IRLM
>stats command for 2 of our systems with the following results but I don't
know
>what to do from here to translate that in to the MLMT parameter value. I'd
>like to have an idea of if the default value of 2 will be large enough to handle
>our locks.
>
>F DB2TIRLM,STATUS,STOR
>DXR100I DJ2T001 STOR STATS 627
>PC: NO MAXCSA: 15M LTE: 4M RLE: 38552 RLEUSE: 1310
>CSA USE: ACNT: 4612K AHWM: 6404K CUR: 6470K HWM: 8254K
> ABOVE 16M: 114 6470K BELOW 16M: 0 0K
>CLASS TYPE SEGS MEM TYPE SEGS MEM TYPE SEGS MEM
>ACCNT T-1 64 4096K T-2 8 512K T-3 1 4K
>PROC WRK 7 42K SRB 2 2K OTH 2 2K
>MISC VAR 29 1913K N-V 6 22K FIX 1 24K
> DXR100I End of display
>
>
>F DB3PIRLM,STATUS,STOR
>DXR100I DJ3P003 STOR STATS 262
>PC: NO MAXCSA: 15M LTE: 16M RLE: 143360 RLEUSE: 3268
>CSA USE: ACNT: 8520K AHWM: 8520K CUR: 10M HWM: 12M
> ABOVE 16M: 225 10M BELOW 16M: 0 0K
>CLASS TYPE SEGS MEM TYPE SEGS MEM TYPE SEGS MEM
>ACCNT T-1 120 7680K T-2 13 832K T-3 2 8K
>PROC WRK 11 66K SRB 33 33K OTH 15 15K
>MISC VAR 30 3833K N-V 92 108K FIX 2 36K
> DXR100I End of display
>
>Thanks,
>Donna Domovic
>

______________________________________________________________________

* IDUG 2009 Denver, CO, USA * May 11-15, 2009 * http://IDUG.ORG/lsNA *
______________________________________________________________________



The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at http://www.idug.org/lsidug under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services at http://www.idug.org/lsms