IDS Forum

RE: Question on SHMVIRTSIZE

Posted By: Jack Parker
Date: Tuesday, 8 May 2007, at 12:55 p.m.

In Response To: RE: Question on SHMVIRTSIZE (Mary Gregory)

I started to reply to this and then put it aside while I dealt with other
issues.

Certainly the easiest way to determine if it benefits is to run a benchmark
on a clean box, and then add the memory and re-run the benchmark. Alas that
is not always possible.

I would be more apt to determine if there was a performance issue first that
I am trying to address and then look at the resources required to resolve
that issue - of which memory could well be a resource.

In a vacuum, you might ask yourself, what is happening with the memory that
we are using? Are we exercising all of it?

Certainly your cache hit rate is lowish and you have high bufwaits and
latchwaits. But if there is no preceived issue, then I would leave well
enough alone.

j.

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org]On Behalf Of
Mary Gregory
Sent: Tuesday, May 08, 2007 12:07 PM
To: ids@iiug.org
Subject: RE: Question on SHMVIRTSIZE [9094]

I still haven't found a good way to determine whether or not adding more
virtual memory to the instance would speed up queries or not. I think I
might try to add another 128 MB just to see what happens. Also, I am
thinking about adding some more BUFFERS but I am trying to be very
cautious about not increasing my checkpoint times. From what I see
right now, everything is performing really well and I don't really need
to make any changes but you all might see something I don't. (I removed
some of the onconfig file parameters to save a little space.)

ONCONFIG PARAMETERS

ROOTNAME a_rootdbs # Root dbspace name
ROOTPATH /dev/inf/chunk001 # Path for device containing root
dbspace
ROOTOFFSET 0 # Offset of root dbspace into device
(Kbytes)
ROOTSIZE 500000 # Size of root dbspace (Kbytes)
PHYSDBS a_plogdbs # Location (dbspace) of physical log
PHYSFILE 100000 # Physical log file size (Kbytes)
LOGFILES 41 # Number of logical log files
LOGSIZE 50000 # Logical log size (Kbytes)
SERVERNUM 1 # Unique id corresponding to a OnLine
instance
DBSERVERNAME online_shm # Name of default database server
DBSERVERALIASES online_tcp # List of alternate dbservernames
NETTYPE ipcshm,3,75,CPU # Configure poll thread(s) for nettype
NETTYPE soctcp,6,200,NET # Configure poll thread(s) for nettype
DEADLOCK_TIMEOUT 240 # Max time to wait of lock in
distributed env.
RESIDENT 1 # Forced residency flag (Yes = 1, No =
0)
MULTIPROCESSOR 1 # 0 for single-processor, 1 for
multi-processor
NUMCPUVPS 5 # Number of user (cpu) vps
SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vps
to one
NOAGE 1 # Process aging
AFF_SPROC 0 # Affinity start processor
AFF_NPROCS 0 # Affinity number of processors
LOCKS 500000 # Maximum number of locks
BUFFERS 155000 # Maximum number of shared buffers
NUMAIOVPS 2 # Number of IO vps
PHYSBUFF 64 # Physical log buffer size (Kbytes)
LOGBUFF 64 # Logical log buffer size (Kbytes)
CLEANERS 64 # Number of buffer cleaner processes
SHMBASE 0x0 # Shared memory base address
SHMVIRTSIZE 1792000 # initial virtual shared memory segment
size
SHMADD 256000 # Size of new shared memory segments
(Kbytes)
SHMTOTAL 0 # Total shared memory (Kbytes).
0=>unlimited
CKPTINTVL 600 # Check point interval (in sec)
LRUS 64 # Number of LRU queues
LRU_MAX_DIRTY 4.000 # LRU percent dirty begin cleaning limit
LRU_MIN_DIRTY 2.000 # LRU percent dirty end cleaning limit
TXTIMEOUT 0x12c # Transaction timeout (in sec)
STACKSIZE 64 # Stack size (Kbytes)

DYNAMIC_LOGS 2
LTXHWM 40
LTXEHWM 55

# Read Ahead Variables
RA_PAGES 20 # Number of pages to attempt to read
ahead
RA_THRESHOLD 8 # Number of pages left before next group

DBSPACETEMP
tempdbs1,tempdbs2,tempdbs3,tempdbs4,tempdbs5,tempdbs6,tempdbs7

FILLFACTOR 90 # Fill factor for building indexes

# Parallel Database Queries (pdq)
MAX_PDQPRIORITY 0 # Maximum allowed pdqpriority
#DS_MAX_QUERIES # Maximum number of decision support
queries
#DS_TOTAL_MEMORY # Decision support memory (Kbytes) TURN THIS
OFF AFTER THE IMPORT
DS_TOTAL_MEMORY # Decision support memory (Kbytes) TURN
THIS OFF AFTER THE IMPORT
DS_MAX_SCANS 1048576 # Maximum number of decision support
scans
DATASKIP off
OPTCOMPIND 2 # To hint the optimizer
DIRECTIVES 1 # Optimizer DIRECTIVES ON (1/Default) or
OFF (0)
ONDBSPACEDOWN 2 # Dbspace down option: 0 = CONTINUE, 1 =
ABORT, 2 = WAIT
OPCACHEMAX 0 # Maximum optical cache size (Kbytes)
# HETERO_COMMIT (Gateway participation in distributed transactions)
# 1 => Heterogeneous Commit is enabled
# 0 (or any other value) => Heterogeneous Commit is disabled
HETERO_COMMIT 0
BLOCKTIMEOUT 3600 # Default timeout for system block
SYSALARMPROGRAM /home/informix/9.40/etc/evidence.sh # System Alarm
program path
# Optimization goal: -1 = ALL_ROWS(Default), 0 = FIRST_ROWS
OPT_GOAL -1
ALLOW_NEWLINE 0 # embedded newlines(Yes = 1, No = 0 or
anything but 1)
BAR_BSALIB_PATH /opt/omni/lib/libob2informix_64bit.sl
DS_MAX_QUERIES 6 # Maximum number of decision support
queries

ONSTAT -P

IBM Informix Dynamic Server Version 9.40.FC4 -- On-Line -- Up 4 days
14:29:2
2 -- 2196484 Kbytes

Profile
dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
535710112 1308089992 17065711597 96.86 31296277 73506490 243924199
87.17

isamtot open start read write rewrite delete commit
rollbk
12889143879 61483810 410801398 10058850470 60258603 10476107 6562628
9953760 3
732

gp_read gp_write gp_rewrt gp_del gp_alloc gp_free gp_curs
0 0 0 0 0 0 0

ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes
0 0 0 157714.53 101146.03 1047 2882

bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans
34018215 3531 16248413925 10 0 2150 3447796
2746919

ixda-RA idx-RA da-RA RA-pgsused lchwaits
137210564 13433495 105455888 253872383 7973596

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
Robert Roussey(IT)
Sent: Wednesday, May 02, 2007 5:14 PM
To: ids@iiug.org
Subject: RE: Question on SHMVIRTSIZE [9061]

If you know the session of the batch job, you can see what pieces of
memory it is using with "onstat -g mem".
"onstat -g ses" will show all sessions and their total use of SHM.
If you are using PDQ for the batch job, you should see it reflected by
getting snapshots of "onstat -g mgm" while it is running.

Maybe post your ONCONFIG file and people can comment on it as well as
a 24hr snapshot of "onstat -p".

Bob Roussey
Unix / Informix Administration
Spirit Airlines
Robert.Roussey@SpiritAir.com

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Messages In This Thread

• Question on SHMVIRTSIZE
  Mary Gregory -- Monday, 30 April 2007, at 2:33 p.m.
  • RE: Question on SHMVIRTSIZE
    Robert Roussey\(IT\) -- Monday, 30 April 2007, at 4:29 p.m.
    • RE: Question on SHMVIRTSIZE
      Mary Gregory -- Monday, 30 April 2007, at 4:37 p.m.
      • Re: Question on SHMVIRTSIZE
        DL Redden -- Monday, 30 April 2007, at 10:08 p.m.
        • RE: Question on SHMVIRTSIZE
          Mary Gregory -- Tuesday, 1 May 2007, at 9:19 a.m.
          • Re: Question on SHMVIRTSIZE
            Andreas Breitfeld -- Wednesday, 2 May 2007, at 10:55 a.m.
          • RE: Question on SHMVIRTSIZE
            Robert Roussey\(IT\) -- Wednesday, 2 May 2007, at 6:14 p.m.
            • RE: Question on SHMVIRTSIZE
              Mary Gregory -- Tuesday, 8 May 2007, at 12:06 p.m.
              • RE: Question on SHMVIRTSIZE
                Jack Parker -- Tuesday, 8 May 2007, at 12:55 p.m.
              • Re: Question on SHMVIRTSIZE
                Keith Simmons -- Wednesday, 9 May 2007, at 5:13 a.m.
                • Re: Question on SHMVIRTSIZE
                  ART KAGEL, BLOOMBERG/ 731 LEXIN -- Monday, 14 May 2007, at 12:29 p.m.
                  • Re: Question on SHMVIRTSIZE
                    DL Redden -- Thursday, 17 May 2007, at 4:29 p.m.
                    • Re: Question on SHMVIRTSIZE
                      ART KAGEL, BLOOMBERG/ 731 LEXIN -- Thursday, 17 May 2007, at 6:36 p.m.
                  • RE: Question on SHMVIRTSIZE
                    Mary Gregory -- Monday, 21 May 2007, at 10:06 a.m.
                    • RE: Question on SHMVIRTSIZE
                      ART KAGEL, BLOOMBERG/ 731 LEXIN -- Monday, 21 May 2007, at 12:48 p.m.

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