Monitoring Disk I/O Utilization

Use any of the following utilities to determine if your disk I/O operations are efficient for your applications:

• onstat -g arguments
• ISA
• oncheck utility

Using onstat -g to Monitor I/O Utilization

Use the following onstat -g arguments to monitor disk I/O utilization.

Argument

Description

iof

Displays asynchronous I/O statistics by chunk or file

This argument is similar to the onstat -d, except that information on nonchunk files also appears. This argument displays information about temporary dbspaces and sort files.

iog

Displays asynchronous I/O global information

ioq

Displays asynchronous I/O queuing statistics

iov

Displays asynchronous I/O statistics by virtual processor

For a detailed case study that uses various onstat outputs, see Appendix A. Case Studies and Examples.

Using ISA to Monitor I/O Utilization

You can use ISA to monitor disk I/O utilization. ISA uses information that the following onstat command-line options generate to display session information, as the following table shows.

Using the oncheck Utility to Monitor I/O Utilization

Disk I/O operations are usually the longest component of the response time for a query. Contiguously allocated disk space improves sequential disk I/O operations because the database server can read in larger blocks of data and use the read-ahead feature to reduce the number of I/O operations.

The oncheck utility displays information about storage structures on a disk, including chunks, dbspaces, blobspaces, extents, data rows, system catalog tables, and other options. You can also use oncheck to determine the number of extents that exist within a table and whether or not a table occupies contiguous space.

The oncheck utility provides the following options and information that apply to contiguous space and extents. For information on how to use other oncheck options, see the IBM Informix: Dynamic Server Administrator's Guide.

For more information about using oncheck to monitor space, see Estimating Table Size. For more information on concurrency during oncheck execution, see Improving Performance for Index Checks. For more oncheck information, see your IBM Informix: Administrator's Reference.