i/o polling process count

i/o polling process count specifies the maximum number of processes that SAP ASE can run before the scheduler checks for disk and network I/O completions. Tuning i/o polling process count affects both the response time and throughput of SAP ASE.

Summary Information

Default value


Range of values

1 – 2147483647



Display level


Required role

System administrator

Configuration group

SQL Server Administration

Note: i/o polling process count functions only when you configure SAP ASE for process kernel mode; it is nonfunctional for threaded kernel mode.
SAP ASE checks for disk or network I/O completions:

As a general rule, increasing the value of i/o polling process count increases throughput for applications that generate a lot of disk and network I/O. Conversely, decreasing the value improves process response time in these applications, possibly at the risk of lowering throughput.

If your applications create both I/O and CPU-bound tasks, tuning i/o polling process count to a low value (1 – 2) ensures that I/O-bound tasks get access to CPU cycles.

For OLTP applications (or any I/O-bound application with user connections and short transactions), tuning i/o polling process count to a value in the range of 20 – 30 may increase throughput, but may also increase response time.

When tuning i/o polling process count, consider these other parameters:

Use sp_sysmon to determine the effect of changing i/o polling process count. See the Performance and Tuning Series: Monitoring SAP Adaptive Server with sp_sysmon.