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 UNIX VMSTAT Utility to the Rescue
Oracle Tips by Burleson Consulting

Advanced Oracle Utilities: The Definitive Reference by Rampant TechPress is written by the top Oracle database experts (Bert Scalzo, Donald Burleson, and Steve Callan).  The following is an excerpt from the book.

Vmstat to the Rescue

The UNIX vmstat utility is especially useful for monitoring the performance of Oracle databases. Vmstat can be found on almost all implementations of UNIX, including Linux. Run vmstat using the simple UNIX daemon process shown in Listing 4.1.


       Listing 4.1 – vmstat capture script


#  This is the Linux version

# First, we must set the environment . . . .


ORACLE_HOME=`cat /etc/oratab|grep \^$ORACLE_SID:|cut -f2 -d':'`


export PATH

MON=`echo ~oracle/mon`
export MON

SERVER_NAME=`uname -a|awk '{print $2}'`
typeset -u SERVER_NAME


# sample every five minutes (300 seconds) . . . .


while true

   vmstat ${SAMPLE_TIME} 2 > /tmp/msg$$


# run vmstat and direct the output into the Oracle table . . . 

cat /tmp/msg$$|sed 1,3d | awk  '{ printf("%s %s %s %s %s %s\n", $1, $8, $9, $14, $15, $16) }' | while read RUNQUE PAGE_IN PAGE_OUT USER_CPU SYSTEM_CPU IDLE_CPU

      $ORACLE_HOME/bin/sqlplus -s system/manager@testb1<<EOF

      insert into sys.mon_vmstats
                           values (



rm /tmp/msg$$


This daemon collects server performance information every five minutes (300 seconds) and stores the server data inside Oracle tables. These Oracle vmstat tables, once populated, can give interesting details about the server. For example, one can find out usage information about how much RAM and disk I/O is being used on the database server, as well as how many CPUs are being used.

When analyzing vmstat output, there are several metrics to which the DBA should pay attention. For example, keep an eye on the CPU run queue column. The run queue should never exceed the number of CPUs on the server. If it is noticed that the run queue starts exceeding the amount of CPUs, it is a good indication that the server has a CPU bottleneck.

To get an idea of the RAM usage on the server, watch the page-in (pi) and page-out (po) columns of vmstat’s output. By tracking common virtual memory operations such as page-outs, this infers the times that the Oracle database is performing a lot of work. Even though UNIX page-ins must correlate with the vmstat’s refresh rate to accurately predict RAM swapping, plotting page-ins can tell when the server is having spikes of RAM usage.

Once captured, it is very easy to take the information about server performance directly from the Oracle tables and plot them in a trend graph. Rather than using an expensive statistical package such as SAS, use Microsoft Excel. Copy and paste the data from the tables into Excel. After that, use the Chart Wizard to create a line chart that will help view server usage information and discover trends.

For more details on Oracle utilities, see the book "Advanced Oracle Utilities" by Bert Scalzo, Donald K. Burleson, and Steve Callan.

You can buy it direct from the publisher for 30% off directly from Rampant TechPress.


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