SERVGSZ parameter

ATB server size maximum

Summary

Default value

0

Parameter type

System

Where set

On User 0's parameter line

Related products

All

Introduced

Model 204 V7.5

Description

The SERVGSZ parameter, along with the SERVGA parameter, controls swappable above-the-bar (in memory with address greater than 2G) server areas.

• SERVGSZ (server non-swappable size) is the amount of space in bytes required for the swappable above-the-bar server tables per server. The total amount of storage allocated for swappable above-the-bar server areas equals SERVGSZ rounded to 4K and multiplied by NSERVS. When sizing SERVGSZ you should use the largest sum of swappable above-the-bar server table sizes that might be needed.
• SERVGA (server swappable areas) indicates the server tables that you want to be above the bar.
• The SERVNSSZ parameter controls the size of the non-swappable above-the-bar server areas.

While it might seem odd to have above-the-bar swappable server areas, especially if swapping to above-the-bar memory, placing NTBL and QTBL in a swappable area can save quite a bit of real memory. This is especially true if the RESPAGE parameter is set to a non-zero value and there are significantly more users (NUSERS) than servers (NSERVS). In such a case, most swapped out users would either be using a resident (shared) NTBL and QTBL, or they would be logged out and only using a single 4K page. As such, reserving the amount of space required for NTBL and QTBL (which can typically get quite large) in the non-swappable above-the-bar area for all the swapped out users can waste a significant amount of real storage.