This file is read by sa1(8) and sa2(8) shell scripts from the
sysstat's set of tools. It consists of a sequence of shell
variable assignments used to configure sysstat logging. The
variables and their meanings are:
COMPRESSAFTER
Number of days after which daily data files are to be
compressed. The compression program is given in the ZIP
variable.
DELAY_RANGE
Tell sa2 script to wait for a random delay in the
indicated range before running. This delay is expressed
in seconds, and is aimed at preventing a massive I/O burst
at the same time on VM sharing the same storage area. A
value of 0 means that sa2 script will generate its reports
files immediately.
HISTORY
The number of days during which a daily data file or a
report should be kept. Data files or reports older than
this number of days will be removed by the sa2(8) shell
script. Data files and reports are normally saved in the
/var/log/sa directory, under the name saDD (for data
files) or sarDD (for reports), where the DD parameter
indicates the current day.
The number of files actually kept in the /var/log/sa
directory may be slightly higher than the HISTORY value
due to the way the sa2 script figures out which files are
to be removed (see below "How the sa2(8) script applies
HISTORY value"). Using a value of 28 keeps a whole month's
worth of data. If you set HISTORY to a value greater than
28 then you should consider using sadc's option -D to
prevent older data files from being overwritten (see
sadc(8) manual page). In this latter case data files are
named saYYYYMMDD and reports sarYYYYMMDD, where YYYY
stands for the current year, MM for the current month and
DD for the current day.
How the sa2(8) script applies HISTORY value
The sa2 script uses the find command with the -mtime
option to figure out which files are to be removed. The
find command interprets this value as "N 24 hour periods",
ignoring any fractional part. This means that the last
modified time of a given sa[r]DD data or report file,
using a HISTORY of 1, has to have been modified at least
two days ago before it will be removed. And for a HISTORY
of 28 that would mean 29 days ago.
To figure out how a HISTORY of 28 is applied in practice,
we need to consider that the sa2 script that issues the
find command to remove the old files typically runs just
before mid-night on a given system, and since the first
record from sadc can also be written to the previous day's
data file (thereby moving its modification time up a bit),
the sa2 script will leave 30 files untouched. So for a
setting of 28, and counting the data file of the current
day, there will always be 31 files (or 30 files, depending
on the number of days in a month) in the /var/log/sa
directory during the majority of a given day. E.g.:
April 30th: 31 files (Apr 30th-1st, Mar 31th)
May 1st: 30 files (May 1st, Apr 30th-2nd)
Yet we can note the following exceptions (as inspected at
Noon of the given day):
February 28th: 31 files (Feb 28th-1st, Jan 31st, 30th &
29th)
March 1st: 30 files (Mar 1st, Feb 28th-2nd, Jan 31st &
30th)
March 2nd: 29 files (Mar 1st & 2nd, Feb 28th-3rd, Jan.
31st)
March 3rd: 28 files (Mar 1st-3rd, Feb 28th-4th)
March 4th - March 28th: 28 files
March 29th: 29 files
March 30th: 30 files
March 31st: 31 files
(Determining the number of files in March on a leap year
is left as an exercise for the reader).
Things are simpler if you use the sa[r]YYYYMMDD name
format. Apply the same logic as above in this case and
you will find that there are always HISTORY + 3 files in
the /var/log/sa directory during the majority of a given
day.
REPORTS
Set this variable to false to prevent the sa2 script from
generating reports (the sarDD files).
SA_DIR Directory where the standard system activity daily data
and report files are saved. Its default value is
/var/log/sa.
SADC_OPTIONS
Options that should be passed to sadc(8). With these
options (see sadc(8) manual page), you can select some
additional data which are going to be saved in daily data
files. These options are used only when a new data file
is created. They will be ignored with an already existing
one.
YESTERDAY
By default sa2 script generates yesterday's summary, since
the cron job usually runs right after midnight. If you
want sa2 to generate the summary of the same day (for
example when cron job runs at 23:53) set this variable to
no.
ZIP Program used to compress data and report files.
