sar Command

Purpose

Collects, reports, or saves system activity information.

Syntax

/usr/sbin/sar [ { -A [ -M ] | [ -a ] [ -b ] [ -c ] [ -d ][ -k ] [ -m ] [ -q ] [ -r ] [ -u ] [ -v ] [ -w ] [ -y ] [ -M ] } ] [ -P processoridentifier, ... | ALL | RST [-O {sortcolumn=col_name[,sortorder={asc|desc}][,topcount=n]}]]] [ [ -@ wparname ] [ -e[YYYYYMMDD]hh [ :mm [ :ss ] ] ] [ -ffile ] [ -iseconds ] [ -ofile ] [ -s[YYYYYMMDD]hh [ :mm [:ss ] ] ][-x] [ Interval [ Number ] ]

sar [-X [-o filename]] [interval[count]]

Description

The sar command writes to standard output the contents of selected cumulative activity counters in the operating system. The accounting system, based on the values in the number and interval parameters, writes information the specified number of times spaced at the specified intervals in seconds. The default sampling interval for the number parameter is 1 second. The collected data can also be saved in the file specified by the -o file flag.

The sar command generates an XML file when the –X option is specified.

The sar command extracts and writes to standard output records previously saved in a file. This file can be either the one specified by the -f flag or, by default, the standard system activity daily data file, the /var/adm/sa/sadd file, where the dd parameter indicates the current day.

Without the -P flag, the sar command reports system-wide (global among all processors) statistics, which are calculated as averages for values expressed as percentages, and as sums otherwise. If the -P flag is given, the sar command reports activity which relates to the specified processor or processors. If -P ALL is given, the sar command reports statistics for each individual processor, followed by system-wide statistics. If -P ALL is used in a workload partition environment and the WPAR is associated with an rset registry, the resource set statistics and the system-wide statistics are displayed; the processors that belong to the resource set are prefixed with an asterisk symbol (*).

You can select information about specific system activities using flags. If you do not specify any flags, you select only system and WPAR unit activity. Specifying the -A flag selects all activities. The sar command prints the number of processors and the number of disks that are currently active before starting to print the statistics.

The default version of the sar command (processor utilization report) might be one of the first facilities the user runs to begin system activity investigation, because it monitors major system resources. If processor utilization is near 100 percent (user + system), the workload sampled is processor-bound. If a considerable percentage of time is spent in I/O wait, it implies that processor execution is blocked waiting for disk I/O. The I/O may be required file accesses or it may be I/O associated with paging due to a lack of sufficient memory.

Methods Used to Compute CPU Disk I/O Wait Time

AIX® 4.3.3 and later contains enhancements to the method used to compute the percentage of processor time spent waiting on disk I/O (wio time). The method used in AIX 4.3.2 and earlier versions of the operating system can, under certain circumstances, give an inflated view of wio time on SMPs. The wio time is reported by the commands sar (%wio), vmstat (wa) and iostat (% iowait).

The method used in AIX 4.3.2 and earlier versions is as follows: At each clock interrupt on each processor (100 times a second per processor), a determination is made as to which of the four categories (usr/sys/wio/idle) to place the last 10 ms of time. If the processor was busy in usr mode at the time of the clock interrupt, then usr gets the clock tick added into its category. If the processor was busy in kernel mode at the time of the clock interrupt, then the sys category gets the tick. If the processor was not busy, a check is made to see if any I/O to disk is in progress. If any disk I/O is in progress, the wio category is incremented. If no disk I/O is in progress and the processor is not busy, the idle category gets the tick. The inflated view of wio time results from all idle processors being categorized as wio regardless of the number of threads waiting on I/O. For example, systems with just one thread doing I/O could report over 90 percent wio time regardless of the number of processors it has.

The method used in operating system AIX 4.3.3 and later is as follows: The change in operating system AIX 4.3.3 is to only mark an idle processor as wio if an outstanding I/O was started on that processor. This method can report much lower wio times when just a few threads are doing I/O and the system is otherwise idle. For example, a system with four processors and one thread doing I/O will report a maximum of 25 percent wio time. A system with 12 processors and one thread doing I/O will report a maximum of 8 percent wio time. NFS client reads/writes go through the VMM, and the time that biods spend in the VMM waiting for an I/O to complete is now reported as I/O wait time.

If multiple samples and multiple reports are desired, it is convenient to specify an output file for the sar command. Direct the standard output data from the sar command to /dev/null and run the sar command as a background process. The syntax for this is:

sar -A -o data.file interval count > /dev/null &

All data is captured in binary form and saved to a file (data.file). The data can then be selectively displayed with the sar command using the -f option.

The sar command calls a process named sadc to access system data. Two shell scripts (/usr/lib/sa/sa1 and /usr/lib/sa/sa2) are structured to be run by the cron command and provide daily statistics and reports. Sample stanzas are included (but commented out) in the /var/spool/cron/crontabs/adm crontab file to specify when the cron daemon should run the shell scripts. Collection of data in this manner is useful to characterize system usage over a period of time and determine peak usage hours.

You can insert a dummy record into the standard system activity daily data file at the time of system start by un-commenting corresponding lines in the /etc/rc script. The sar command reports time change not positive for any record where processor times are less than the previous record. This occurs if you reboot the system with the dummy record insertion lines in /etc/rc commented out.

Beginning with AIX 5.3, the sar command reports utilization metrics physc and %entc which are related to Micro-Partitioning® and simultaneous multithreading environments. These metrics will only be displayed on Micro-Partitioning and simultaneous multithreading environments. physc indicates the number of physical processors consumed by the partition (in case of system wide utilization) or logical processor (if the -P flag is specified) and %entc indicates the percentage of the allocated entitled capacity (in case of system wide utilization) or granted entitled capacity (if the -P flag is specified). When the partition runs in capped mode, the partition cannot get more capacity than it is allocated. In uncapped mode, the partition can get more capacity than it is actually allocated. This is called granted entitled capacity. If the -P flag is specified and there is unused capacity, sar prints the unused capacity as separate processor with cpu id U.

Beginning with AIX 6.1, the sar command reports the utilization metric %resc, which is related to the workload partition (WPAR) environment. The %resc metric indicates the percentage of processor resource that the WPAR consumes. This field is displayed only if the processor-resource limit is enforced in the WPAR. The sar -P command reports the resource set (RSET) utilization metrics R for the WPAR.

You can use the System application in Web-based System Manager (wsm) to run this command.

You could also use the System Management Interface Tool (SMIT) smit sar fast path to run this command.

Flags

Security

Access Control: These commands should grant execute (x) access only to members of the adm group.

Examples

1. To report system unit activity, enter the following command:

   sar

2. To report current tty activity for each 2 seconds for the next 40 seconds, enter the following command:

   sar  -y  -r 2 20

3. To watch system unit for 10 minutes and sort data, enter the following command:

   sar  -o temp 60 10

4. To report processor activity for the first two processors, enter the following command:

   sar  -u  -P 0,1

   This produces output similar to the following:

   cpu  %usr  %sys  %wio  %idle
   0      45    45     5      5
   1      27    65     3      5

5. To report message, semaphore, and processor activity for all processors and system-wide, enter the following command:

   sar  -mu  -P ALL

   On a four-processor system, this produces output similar to the following (the last line indicates system-wide statistics for all processors) :

   cpu  msgs/s  sema/s  %usr  %sys  %wio  %idle
   0      7       2       45    45     5     5
   1      5       0       27    65     3     5
   2      3       0       55    40     1     4
   3      4       1       48    41     4     7
   -     19       3       44    48     3     5

6. To see physical processor consumed and entitlement consumed for all processors system-wide, run sar command in a shared processor logical partition machine, as follows:

   sar –P ALL

   On a two-logical processor system, this produces output similar to the following (the last line indicates system-wide statistics for all processors, and the line with cpuid U indicates the system-wide Unused capacity):

   cpu    %usr    %sys    %wio   %idle   physc   %entc
    0        0       0       0     100    0.02     3.1
    1        0       0       0     100    0.00     1.0
    U        -       -       0      96    0.48    96.0
    -        0       0       0     100    0.02     4.0

7. To report system call, kernel process, and paging activities with separate headers for each of the three lines of data at each iteration for every 2 seconds for the next 40 seconds, enter the following command:

   sar -Mckr 2 20

8. To report all activities with multiple sets of headers for every 2 seconds for the next 40 seconds, enter the following command:

   sar -MA 2 20

9. To report the processor use statistics in a WPAR from the global environment, enter the following command:

   sar -@ wparname

10. To report the processor activities for all of the processors present in the rset registry associated with the WPAR from inside a WPAR, enter the following command:

    sar -P RST 1 1

    In a WPAR that is associated with an RSET of two logical processors, the previous command generates a report similar to the following:

    19:34:39 cpu    %usr    %sys    %wio   %idle   physc
    19:34:40  0        0       2       0      98    0.54
              1        0       0       0     100    0.46
              R        0       1       0      99    1.00

11. To report all of the processor activities from inside a WPAR, enter the following command:

    sar -P ALL 1 1

    In a WPAR that is associated with an RSET of two logical processors, the previous command generates a report similar to the following:

    19:34:39 cpu    %usr    %sys    %wio   %idle   physc
    19:34:40 *0        0       2       0      98    0.54
             *1        0       0       0     100    0.46
              R        0       1       0      99    1.00
              -        0       1       0      99    1.00

12. To display the sorted output for the column cswch/s with the –w flag, enter the following command:

    sar -w -P ALL  -O sortcolumn=cswch/s 1 1 

13. To list the top ten CPUs, sorted on the scall/s column, enter the following command:

    sar -c -O sortcolumn=scall/s,sortorder=desc,topcount=10 -P ALL 1

Files