SERVGSZ parameter

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ATB server size maximum


Default value
Parameter type
Where set
On User 0's parameter line
Related products
Model 204 V7.5


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

  • SERVGSZ (server 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.

For reference purposes:

  • The SERVNSSZ parameter controls the size of the non-swappable above-the-bar server areas.
  • The SERVNSA parameter controls which tables are in 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.