RA_PAGES

onconfig.std
value

None

if not present

4 if MULTIPROCESSOR is 0;
8 if MULTIPROCESSOR is 1

units

Number of data pages

range of values

RA_THRESHOLD through BUFFERS

takes effect

When shared memory is initialized

utilities

onutil

refer to

The following material:

• Configuring the database server to read ahead in the shared-memory chapter of the IBM Informix: Administrator's Guide
• Calculating RA_PAGES and RA_THRESHOLD in your IBM Informix: Performance Guide

RA_PAGES specifies the number of disk pages to attempt to read ahead during sequential scans of data records. Read-ahead can greatly speed up database processing by compensating for the slowness of I/O processing relative to the speed of CPU processing.

This parameter works with the RA_THRESHOLD parameter. Specifying values that are too large can result in excessive buffer-caching activity.

To modify the RA_PAGES parameter dynamically, use the onutil SET command. Example:

%onutil
 RA_PAGES 32;