Table-Location Guidelines

This section lists some strategies for optimizing the disk layout, given certain characteristics about the tables in a database. You can implement many of these strategies with a higher degree of control using table fragmentation:

• Isolate high-use tables on a separate disk.

  To isolate a high-use table on its own disk device, assign the device to a chunk, and assign the same chunk to a dbspace. Finally, place the frequently used table in the dbspace just created using the IN dbspace option of CREATE TABLE.

  To display the level of I/O operations against each chunk, run the onstat -g iof option.

• Fragment high-use tables over multiple disks.
• Group related tables in a dbspace.

  If a device that contains a dbspace fails, all tables in that dbspace are inaccessible. However, tables in other dbspaces remain accessible. Although you must perform a cold restore if a dbspace that contains critical information fails, you need only perform a warm restore if a noncritical dbspace fails.

• Place high-use tables on the middle partition of a disk.
• Optimize table extent sizes.

For more information, see the chapter on table performance considerations in your IBM Informix Performance Guide. For information on onstat options, see the IBM Informix Administrator's Reference.