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Informix 7.31 not using read cache

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chrisak

Technical User
Aug 19, 2002
1
US
We have an Informix 7.31 database running on an IBM RS/6000 M80 with 8 cpus and 8 GBytes of RAM. Everything seems to function okay but the performance should be a lot better. We noticed that when we run onstat we get output like:

Profile
dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
3152145294 1403143001 247495989 0.00 7292018 14505011 241739734 96.98

It seems like the server isn't caching reads at all. We've adjusted the onconfig numerous times with no success. Here is the current onconfig:
Any suggestions?

#**************************************************************************
#
# INFORMIX SOFTWARE, INC.
#
# Title: onconfig.std
# Description: Informix Dynamic Server Configuration Parameters
#
#**************************************************************************

# Root Dbspace Configuration

ROOTNAME rootdbs # Root dbspace name
ROOTPATH /dev/rlv02_1 # Path for device containing root dbspace
ROOTOFFSET 4 # Offset of root dbspace into device (Kbytes)
ROOTSIZE 512000 # Size of root dbspace (Kbytes)

# Disk Mirroring Configuration Parameters

MIRROR 0 # Mirroring flag (Yes = 1, No = 0)
MIRRORPATH # Path for device containing mirrored root
MIRROROFFSET 0 # Offset into mirrored device (Kbytes)

# Physical Log Configuration

PHYSDBS rootdbs # Location (dbspace) of physical log
#PHYSFILE 16000 # Physical log file size (Kbytes)
PHYSFILE 32000 # Physical log file size (Kbytes)

# Logical Log Configuration

LOGFILES 6 # Number of logical log files
#LOGSIZE 1200 # Logical log size (Kbytes)
LOGSIZE 12000 # Logical log size (Kbytes)

# Diagnostics

MSGPATH /usr/informix/online.log # System message log file path
CONSOLE /dev/console # System console message path
#ALARMPROGRAM /usr/informix/etc/log_full.sh # Alarm program path
ALARMPROGRAM # Alarm program path
SYSALARMPROGRAM /usr/informix/etc/evidence.sh # System Alarm program path
TBLSPACE_STATS 1

# System Archive Tape Device

TAPEDEV /dev/tapedev # Tape device path
TAPEBLK 512 # Tape block size (Kbytes)
TAPESIZE 7000000 # Maximum amount of data to put on tape (Kbytes)


# Log Archive Tape Device

LTAPEDEV /dev/null # Log tape device path
LTAPEBLK 512 # Log tape block size (Kbytes)
LTAPESIZE 7000000 # Max amount of data to put on log tape (Kbytes)


# Optical

STAGEBLOB # Informix Dynamic Server/Optical staging area

# System Configuration

SERVERNUM 40 # Unique id corresponding to a Dynamic Server in
stance
DBSERVERNAME sss4server # Name of default database server
DBSERVERALIASES tcpserver4 # List of alternate dbservernames
#NETTYPE # Configure poll thread(s) for nettype
#not working NETTYPE ipcshm,2,130,CUP # Configure poll thread(s) for n
ettype
#NETTYPE tlitcp,1,,NET # Configure poll thread(s) for nettype
DEADLOCK_TIMEOUT 60 # Max time to wait of lock in distributed env.
RESIDENT 0 # Forced residency flag (Yes = 1, No = 0)

MULTIPROCESSOR 1 # 0 for single-processor, 1 for multi-processor
NUMCPUVPS 6 # 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

# Shared Memory Parameters

#LOCKS 2000 # Maximum number of locks
LOCKS 2400 # 120 User x 20 lock/qry Maximum number of locks

#BUFFERS 10000 # Maximum number of shared buffers
BUFFERS 32000 # 25%x1G/4Kpg Maximum number of shared buffers
#NUMAIOVPS 4 # Number of IO vps
NUMAIOVPS 72 # Number of IO vps Chunks+2-4=74+2-4=72
#PHYSBUFF 64 # Physical log buffer size (Kbytes)
PHYSBUFF 128 # Physical log buffer size (Kbytes)
#LOGBUFF 64 # Logical log buffer size (Kbytes)
LOGBUFF 128 # Logical log buffer size (Kbytes)
LOGSMAX 24 # Maximum number of logical log files
#CLEANERS 4 # Number of buffer cleaner processes
CLEANERS 32 # Number of buffer cleaner processes
SHMBASE 0x700000000000000L # Shared memory base address
SHMVIRTSIZE 255000 # initial virtual shared memory segment size
SHMADD 255000 # Size of new shared memory segments (Kbytes)
#SHMADD 16384 # Size of new shared memory segments (Kbytes)
SHMTOTAL 0 # Total shared memory (Kbytes). 0=>unlimited
CKPTINTVL 300 # Check point interval (in sec)
#LRUS 8 # Number of LRU queues
LRUS 32 # Number of LRU queues
LRU_MAX_DIRTY 60 # LRU percent dirty begin cleaning limit
LRU_MIN_DIRTY 50 # LRU percent dirty end cleaning limit
LTXHWM 50 # Long transaction high water mark percentage
LTXEHWM 60 # Long transaction high water mark (exclusive)
TXTIMEOUT 300 # Transaction timeout (in sec)
#STACKSIZE 32 # Stack size (Kbytes)
STACKSIZE 128 # Stack size (Kbytes)

# System Page Size
# BUFFSIZE - Dynamic Server no longer supports this configuration parameter.
# To determine the page size used by Dynamic Server on your platform
# see the last line of output from the command, 'onstat -b'.


# Recovery Variables
# OFF_RECVRY_THREADS:
# Number of parallel worker threads during fast recovery or an offline restore.
# ON_RECVRY_THREADS:
# Number of parallel worker threads during an online restore.

OFF_RECVRY_THREADS 10 # Default number of offline worker threads
ON_RECVRY_THREADS 1 # Default number of online worker threads

# Data Replication Variables
# DRAUTO: 0 manual, 1 retain type, 2 reverse type
DRAUTO 0 # DR automatic switchover
DRINTERVAL 30 # DR max time between DR buffer flushes (in sec)

DRTIMEOUT 30 # DR network timeout (in sec)
DRLOSTFOUND /usr/informix/etc/dr.lostfound # DR lost+found file path

# CDR Variables
CDR_LOGBUFFERS 2048 # size of log reading buffer pool (Kbytes)
CDR_EVALTHREADS 1,2 # evaluator threads (per-cpu-vp,additional)
CDR_DSLOCKWAIT 5 # DS lockwait timeout (seconds)
CDR_QUEUEMEM 4096 # Maximum amount of memory for any CDR queue (Kbytes)
CDR_LOGDELTA 30 # % of log space allowed in queue memory
CDR_NUMCONNECT 16 # Expected connections per server
CDR_NIFRETRY 300 # Connection retry (seconds)
CDR_NIFCOMPRESS 0 # Link level compression (-1 never, 0 none, 9 max)

# Backup/Restore variables
BAR_ACT_LOG /tmp/bar_act.log
BAR_MAX_BACKUP 0
BAR_RETRY 1
BAR_NB_XPORT_COUNT 10
BAR_XFER_BUF_SIZE 31

# Informix Storage Manager variables
ISM_DATA_POOL ISMData # If the data pool name is changed, be sure to
# update $INFORMIXDIR/bin/onbar. Change to
# ism_catalog -create_bootstrap -pool <new name>

ISM_LOG_POOL ISMLogs

# Read Ahead Variables
#RA_PAGES 20 # Number of pages to attempt to read ahead
RA_PAGES 200 # Number of pages to attempt to read ahead
#RA_THRESHOLD 10 # Number of pages left before next group
RA_THRESHOLD 180 # Number of pages left before next group

# DBSPACETEMP:
# Dynamic Server equivalent of DBTEMP for SE. This is the list of dbspaces
# that the Dynamic Server SQL Engine will use to create temp tables etc.
# If specified it must be a colon separated list of dbspaces that exist
# when the Dynamic Server system is brought online. If not specified, or if
# all dbspaces specified are invalid, various ad hoc queries will create
# temporary files in /tmp instead.

DBSPACETEMP tempdbs # Default temp dbspaces

# DUMP*:
# The following parameters control the type of diagnostics information which
# is preserved when an unanticipated error condition (assertion failure) occurs
# during Dynamic Server operations.
# For DUMPSHMEM, DUMPGCORE and DUMPCORE 1 means Yes, 0 means No.

DUMPDIR /tmp # Preserve diagnostics in this directory
DUMPSHMEM 1 # Dump a copy of shared memory
DUMPGCORE 0 # Dump a core image using 'gcore'
DUMPCORE 0 # Dump a core image (Warning:this aborts Dynamic
Server)
DUMPCNT 1 # Number of shared memory or gcore dumps for
# a single user's session

FILLFACTOR 80 # Fill factor for building indexes

# method for Dynamic Server to use when determining current time
USEOSTIME 0 # 0: use internal time(fast), 1: get time from OS(slow)

# Parallel Database Queries (pdq)
MAX_PDQPRIORITY 70 # Maximum allowed pdqpriority
DS_MAX_QUERIES # Maximum number of decision support queries
DS_TOTAL_MEMORY # Decision support memory (Kbytes)
DS_MAX_SCANS 1048576 # Maximum number of decision support scans
DATASKIP # List of dbspaces to skip

# OPTCOMPIND
# 0 => Nested loop joins will be preferred (where
# possible) over sortmerge joins and hash joins.
# 1 => If the transaction isolation mode is not
# &quot;repeatable read&quot;, optimizer behaves as in (2)
# below. Otherwise it behaves as in (0) above.
# 2 => Use costs regardless of the transaction isolation
# mode. Nested loop joins are not necessarily
# preferred. Optimizer bases its decision purely
# on costs.
OPTCOMPIND 0 # To hint the optimizer

ONDBSPACEDOWN 2 # Dbspace down option: 0 = CONTINUE, 1 = ABORT, 2 = WAIT

LBU_PRESERVE 0 # Preserve last log for log backup
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

# Optimization goal: -1 = ALL_ROWS(Default), 0 = FIRST_ROWS
OPT_GOAL -1

# Optimizer DIRECTIVES ON (1/Default) or OFF (0)
DIRECTIVES 1

# Status of restartable restore
RESTARTABLE_RESTORE ON
 
Hi Chrisak,

suddenly we have the same phenomene as yours.
onstat -p gives 0% for the read cached
and this started suddenly this night while no activity.
(A script takes onstat -p every 15 minutes).

Do you have an explanation.
Is it still a problem on your site?
onstat -p gives :
Informix Dynamic Server Version 7.31.UD2 -- On-Line -- Up 6 days 22:12:35 -- 778144 Kbytes

Profile
dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
409044106 539128170 401249767 0.00 5190847 11751842 84136008 93.83


Yves
 
Sometimes the counters for the &quot;onstat -p&quot; output just need to be reset. Try running &quot;onstat -z&quot; to reset those counters, then check your output again after a few minutes. You'll find that your &quot;onstat -p&quot; output more accurately reflects your current performance.
 
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