Spotlight on SAP ASE 2.12 - User Guide

Disk I/O Checks

This section reports the total number of disk I/O checks, and the number of checks returning I/O.

Total Checks

"Total Checks" reports the number of times engines checked for disk I/O.

When a task needs to perform I/O, the Adaptive Server engine running that task immediately issues an I/O request and puts the task to sleep, waiting for the I/O to complete. The engine then processes other tasks, if any. It also loops to check for completed I/Os. When the engine finds completed I/Os, it moves the task from the sleep queue to the run queue.

I/O Checks

I/O checks is a subset of the Total Checks.  It reports the number of times when a engine checked for I/O that there was a requested I/O pending or waiting.

* Available only for Adaptive Servers versions prior to 12.5.0.3