AIX, Monitoring, System Admin↑ NMON recordings

One can set up NMON recordings from smit via:

# smitty topas -> Start New Recording -> Start local recording -> nmon

However, the smit panel doesn't list the option needed to get disk IO service times. Specifically, the -d option to collect disk IO service and wait times. Thus, it's better to use the command line with the nmon command to collect and report these statistics. Here's one set of options for collecting the data:

# nmon -AdfKLMNOPVY^ -w 4 -s 300 -c 288 -m /var/adm/nmon

The key options here include:

  • -d Collect and report IO service time and wait time statistics.
  • -f Specifies that the output is in spreadsheet format. By default, the command takes 288 snapshots of system data with an interval of 300 seconds between each snapshot. The name of the output file is in the format of hostname_YYMMDD_HHMM.nmon.
  • -O Includes the Shared Ethernet adapter (SEA) VIOS sections in the recording file.
  • -V Includes the disk volume group section.
  • -^ Includes the FC adapter section (which also measures NPIV traffic on VIOS FC adapters).
  • -s Specifies the interval in seconds between 2 consecutive recording snapshots.
  • -c Specifies the number snapshots that must be taken by the command.

Running nmon using this command will ensure it runs for a full day. And it is therefore useful to start nmon daily using a crontab entry in the root crontab file. For example, using the following script:

# cat /usr/local/collect_nmon.ksh
#!/bin/ksh

LOGDIR="/var/adm/nmon"
PARAMS="-fTNAdKLMOPVY^ -w 4 -s 300 -c 288 -m $LOGDIR"

# LOGRET determines the number of days to retain nmon logs.
LOGRET=365

# Create the nmon folder.
if [ ! -d /var/adm/nmon ] ; then
        mkdir -p $LOGDIR
fi

# Compress previous daily log.
find $LOGDIR -name *.nmon -type f -mtime +1 -exec gzip '{}' \;

# Clean up old logs.
find $LOGDIR -name *nmon.gz -type f -mtime +$LOGRET -exec rm '{}' \;

# Start nmon.
/usr/bin/nmon $PARAMS

Then add the following crontab entry to the root crontab file:

0 0 * * * /usr/local/collect_nmon.ksh >/tmp/collect_nmon.ksh.log 2>&1

To get the recordings thru the NMON Analyser tool (a spreadsheet tool that runs on PCs and generates performance graphs, other output, and is available here), it's recommended to keep the number of intervals less than 300.

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