Locate Areas of High Disk Activity

As you do such activities as archiving, you often want to get a feel not only for what percentage of the job is done, but also for exactly where in the database the program is now working. This is helpful in being able to predict how long something is going to take to complete as well as for getting a feeling for the performance of your system. As disk I/O is the slowest thing that your computer system does, you need to know where your disk input and output are occurring. We've shown a simple script called hotspot in the tbtape -D utility explanation earlier. Let's gussy it up a little and make it a little more useful. The new script is called watch_hot.

INFORMIX 75> cat watch_hot
#!/bin/csh
while ( 1 == 1)

$INFORMIXDIR/bin/tbstat -z
sleep 5
$INFORMIXDIR/bin/tbstat -D | grep /
end

There are not many changes from hotspot, but this script continues until you press BREAK or CONTROL-C, zeroes the statistics between each run, and shows you only the relevant chunk information. You can change the sleep period to whatever you like if you want to use watch_hot for a while and monitor your disk activity. As in the hotspot script, remember that the tbstat -z command will zero out the performance statistics each time it is run (every five seconds in this case).

If you have some programs that are monitoring the statistics, this will no doubt interfere with them. Don't confuse the statistics maintained to monitor performance with the statistics maintained in the UPDATE STATISTICS command in SQL. They are two entirely separate sets of statistics.