Hi,

I am doing a large read operation against a 9.4 UC2 db and have tried increasing the performace by uping my shared mem size, using dual processor, added more tmpdbs. The result is the same time for my report.

Anyone have any other suggestions to increase performance of a sequential read operation?

Thanks.

Here is my onstat -p output:

IBM Informix Dynamic Server Version 9.40.UC2 -- On-Line -- Up 00:06:20 -- 183296 Kbytes

Profile
dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
12519 13139 280939 95.54 60 72 0 0.00

isamtot open start read write rewrite delete commit rollbk
560717 82 40613 119409 0 0 0 0 0

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 30.23 18.90 1 2

bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans
2 0 123161 0 0 0 0 4577

ixda-RA idx-RA da-RA RA-pgsused lchwaits
0 0 2280 2260 27

And also top output:

st pid: 22069; load averages: 1.14, 0.63, 0.33 12:58:52
102 processes: 100 sleeping, 1 running, 1 on cpu
CPU states: 43.5% idle, 42.2% user, 13.9% kernel, 0.3% iowait, 0.0% swap
Memory: 768M real, 175M free, 389M swap in use, 2108M swap free

Your output isn't exactly a large read. The sequential read also small.

Here are your options:

- You can create an index for tables that use sequential scan. You find out which tables by running a set explain on on your query.

- Run update statistics

- The optimizer decides which is the fastest way to get a data and sometimes, sequential scan is faster and index search.

- If you really want an index search, add optimizer directives on your SQL to force using an index search.

- You can load tables to memory by using the SET TABLE <tabname> MEMORY_RESIDENT;


Anyway, send your onconfig file.

Thanks for the relpy. I have since dropped and re-created my indexes and done an update statistics high on the entire db. It does not seem to have made any difference. Here is my onconfig:

# Root Dbspace Configuration

ROOTNAME rootdbs # Root dbspace name
ROOTPATH /ifmxdata/ROOTDBS.000 # Path for device containing root dbspace
ROOTOFFSET 0 # Offset of root dbspace into device (Kbytes)
ROOTSIZE 30720 # Size of root dbspace (Kbytes)

# Disk Mirroring Configuration Parameters

MIRROR 0 # Mirroring flag (Yes = 1, No = 0)
MIRRORPATH /ROOTDBS.000 # Path for device containing mirrored root
MIRROROFFSET 0 # Offset into mirrored device (Kbytes)

# Physical Log Configuration

PHYSDBS rootdbs # Location (dbspace) of physical log
PHYSFILE 10000 # Physical log file size (Kbytes)

# Logical Log Configuration

LOGFILES 16 # Number of logical log files
LOGSIZE 4000 # Logical log size (Kbytes)

# Diagnostics

MSGPATH /opt/informix/etc/online.log # System message log file path
CONSOLE /dev/console # System console message path
ALARMPROGRAM /bin/true
TBLSPACE_STATS 1

# System Archive Tape Device

TAPEDEV /entbkup/CA1/mgrbk20051018113329/Database/ifmxbkup.bak
TAPEBLK 16 # Tape block size (Kbytes)
TAPESIZE 2000000 # Maximum amount of data to put on tape (Kbytes)

# Log Archive Tape Device

LTAPEDEV /entbkup/CA1/mgrbk20051018113329/Database/ifmxlog.bak
LTAPEBLK 16 # Log tape block size (Kbytes)
LTAPESIZE 2000000 # Max amount of data to put on log tape (Kbytes)

# Optical

STAGEBLOB # INFORMIX-OnLine/Optical staging area

# System Configuration

SERVERNUM 8 # Unique id corresponding to a OnLine instance
DBSERVERNAME entrust_unx_shm # Name of default database server
DBSERVERALIASES # List of alternate dbservernames
NETTYPE ipcstr,1,50,CPU
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 2 # Number of user (cpu) vps
SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vps to one

NOAGE 0 # Process aging
AFF_SPROC 0 # Affinity start processor
AFF_NPROCS 0 # Affinity number of processors

# Shared Memory Parameters

LOCKS 10000 # Maximum number of locks
BUFFERS 75000 # Maximum number of shared buffers
NUMAIOVPS 2 # Number of IO vps
PHYSBUFF 32 # Physical log buffer size (Kbytes)
LOGBUFF 32 # Logical log buffer size (Kbytes)
LOGSMAX 20 # Maximum number of logical log files
CLEANERS 2 # Number of buffer cleaner processes
SHMBASE 0x0A000000L # Shared memory base address
SHMVIRTSIZE 20000 # initial virtual shared memory segment size
SHMADD 8192 # 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
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)

# Dynamic Logging
# DYNAMIC_LOGS:
# 2 : server automatically add a new logical log when necessary. (ON)
# 1 : notify DBA to add new logical logs when necessary. (ON)
# 0 : cannot add logical log on the fly. (OFF)
#
# When dynamic logging is on, we can have higher values for LTXHWM/LTXEHWM,
# because the server can add new logical logs during long transaction rollback.
# However, to limit the number of new logical logs being added, LTXHWM/LTXEHWM
# can be set to smaller values.
#
# If dynamic logging is off, LTXHWM/LTXEHWM need to be set to smaller values
# to avoid long transaction rollback hanging the server due to lack of logical
# log space, i.e. 50/60 or lower.

DYNAMIC_LOGS 2

# System Page Size
# BUFFSIZE - OnLine no longer supports this configuration parameter.
# To determine the page size used by OnLine 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: gone with 9.40
DRINTERVAL 30 # DR max time between DR buffer flushes (in sec)
DRTIMEOUT 30 # DR network timeout (in sec)
DRLOSTFOUND /opt/informix/etc/dr.lostfound # DR lost+found file path

# CDR Variables
# CDF_LOGBUFFERS: gone with 9.40
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_NIFCOMPRESS 0 # Link level compression (-1 never, 0 none, 9 max)
CDR_SERIAL 0 # Serial Column Sequence
CDR_DBSPACE # dbspace for syscdr database
CDR_QHDR_DBSPACE # CDR queue dbspace (default same as catalog)
CDR_QDATA_SBSPACE # List of CDR queue smart blob spaces

# CDR_MAX_DYNAMIC_LOGS
# -1 => unlimited
# 0 => disable dynamic log addition
# >0 => limit the no. of dynamic log additions with the specified value.
# Max dynamic log requests that CDR can make within one server session.

CDR_MAX_DYNAMIC_LOGS 0 # Dynamic log addition disabled by default

# Backup/Restore variables
BAR_ACT_LOG /tmp/bar_act.log
BAR_DEBUG_LOG /tmp/bar_dbug.log
BAR_MAX_BACKUP 0
BAR_RETRY 1
BAR_NB_XPORT_COUNT 10
BAR_XFER_BUF_SIZE 31
RESTARTABLE_RESTORE ON
BAR_PROGRESS_FREQ 0

# Informix Storage Manager variables
ISM_DATA_POOL ISMData
ISM_LOG_POOL ISMLogs

# Read Ahead Variables
RA_PAGES 20 # Number of pages to attempt to read ahead
RA_THRESHOLD 14 # Number of pages left before next group

# DBSPACETEMP:
# OnLine equivalent of DBTEMP for SE. This is the list of dbspaces
# that the OnLine SQL Engine will use to create temp tables etc.
# If specified it must be a colon separated list of dbspaces that exist
# when the OnLine 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 tmpdbs

# DUMP*:
# The following parameters control the type of diagnostics information which
# is preserved when an unanticipated error condition (assertion failure) occurs
# during OnLine 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 OnLine)
DUMPCNT 1 # Number of shared memory or gcore dumps for
# a single user's session

FILLFACTOR 90 # Fill factor for building indexes

# method for OnLine 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 100 # 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
# OPTCOMPIND
# 0 => Nested loop joins will be preferred (where
# possible) over sortmerge joins and hash joins.
# 1 => If the transaction isolation mode is not
# "repeatable read", 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 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
# LBU_PRESERVE : gone with 9.40
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

SBSPACENAME # Default smartblob space name - this is where blobs
# go if no sbspace is specified when the smartblob is
# created. It is also used by some datablades as
# the location to put their smartblobs.
SYSSBSPACENAME # Default smartblob space for use by the Informix
# Server. This is used primarily for Informix Server
# system statistics collection.

BLOCKTIMEOUT 3600 # Default timeout for system block
SYSALARMPROGRAM /usr/informix/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)

JVPJAVAHOME # JRE installation root directory
JVPHOME # Krakatoa installation directory
JVPPROPFILE .jvpprops # JVP property file
JDKVERSION # JDK version supported by this server
JVPJAVALIB
JVPJAVAVM libjava.so
JVPCLASSPATH