Apache - How system activity recording or sar works, How Sar Command Functions
How system activity recording or sar works
How Sar Command Functions
How System activity recording or sar works
System activity recording is disabled by default on your system. If you wish to enable it, log in as root, enter the command /usr/lib/sa/sar_enable -y, then shut down and reboot the system. See sar_enable(ADM) for more information.
Once system activity recording has been started on your system, it measures internal activity using a number of counters contained in the kernel. Each time an operation is performed, this increments an associated counter. sar(ADM) can generate reports based on the raw data gathered from these counters. sar reports provide useful information to administrators who wish to find out if the system is performing adequately. sar can either gather system activity data at the present time, or extract historic information collected in data files created by sadc(ADM) (System Activity Data Collector) or sa1(ADM).
If system activity recording has been started, the following crontab entries exist for user sys in the file /usr/spool/cron/crontabs/sys:
0 * * * 0-6 /usr/lib/sa/sa1 20,40 8-17 * * 1-5 /usr/lib/sa/sa1The first sa1 entry produces records every hour of every day of the week. The second entry does the same but at 20 and 40 minutes past the hour between 8 am and 5 pm from Monday to Friday. So, there is always a record made every hour, and at anticipated peak times of activity recordings are made every 20 minutes. If necessary, root can modify these entries using the crontab(C) command.
The output files are in binary format (for compactness) and are stored in /usr/adm/sa. The filenames have the format sadd, where dd is the day of the month.
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