SERVGA parameter: Difference between revisions
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The <var>SERVGA</var> parameter controls which server tables are allocated in the ATB-swappable-server area.</p> | The <var>SERVGA</var> parameter controls which server tables are allocated in the ATB-swappable-server area.</p> | ||
Only NTBL and QTBL can be placed above-the-bar in a swappable area.<br> | |||
Each server table to be allocated in that area is controlled by a bit in <var>SERVGA</var>; if the bit is on, the corresponding server table is allocated in the ATB-swappable-server area. | Each server table to be allocated in that area is controlled by a bit in <var>SERVGA</var>; if the bit is on, the corresponding server table is allocated in the ATB-swappable-server area. | ||
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<table class="thJustBold"> | <table class="thJustBold"> | ||
<tr><th>Bit</th><th>Server table placed above the bar</th><th>Required version of Model 204</th></tr> | <tr><th>Bit</th><th>Server table placed above the bar</th><th>Required version of Model 204</th></tr> | ||
<tr><td><code>X' | <tr><td><code>X'00004000'</code></td><td>NTBL</td><td>7.5 or later</td></tr> | ||
<tr><td><code>X' | <tr><td><code>X'00002000'</code></td><td>QTBL</td><td>7.5 or later</td></tr> | ||
</table> | </table> | ||
<p class="note"><b>Note:</b> The bits corresponding to NTBL and QTBL can also be set in <var>SERVNSA</var> but should not be set in both <var>SERVGA</var> and <var>SERVNSA</var> — if they are, an error message is issued and the Online fails to come up.</p> | |||
<var>[[SERVGSZ parameter|SERVGSZ]]</var> 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 <var>SERVGSZ</var> rounded to 4K and multiplied by <var>[[NSERVS parameter|NSERVS]]</var>. | <var>[[SERVGSZ parameter|SERVGSZ]]</var> 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 <var>SERVGSZ</var> rounded to 4K and multiplied by <var>[[NSERVS parameter|NSERVS]]</var>. | ||
When sizing <var>SERVGSZ</var>, it should accomodate the largest swappable above-the-bar table sizes that might be needed. | When sizing <var>SERVGSZ</var>, it should accomodate the largest swappable above-the-bar table sizes that might be needed. | ||
Some server tables can alternatively be placed above-the-bar in a non-swappable area. This can be indicated with the <var>[[SERVNSA parameter|SERVNSA]]</var> and <var>[[SERVNSSZ parameter|SERVNSSZ]]</var> parameters. | |||
{{Template:SERVGA/SERVGSZ common}} | {{Template:SERVGA/SERVGSZ common}} | ||
Revision as of 20:04, 29 June 2015
Above the bar server areas
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 SERVGA parameter controls which server tables are allocated in the ATB-swappable-server area.
Only NTBL and QTBL can be placed above-the-bar in a swappable area.
Each server table to be allocated in that area is controlled by a bit in SERVGA; if the bit is on, the corresponding server table is allocated in the ATB-swappable-server area.
The bits are:
| Bit | Server table placed above the bar | Required version of Model 204 |
|---|---|---|
X'00004000' | NTBL | 7.5 or later |
X'00002000' | QTBL | 7.5 or later |
Note: The bits corresponding to NTBL and QTBL can also be set in SERVNSA but should not be set in both SERVGA and SERVNSA — if they are, an error message is issued and the Online fails to come up.
SERVGSZ 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, it should accomodate the largest swappable above-the-bar table sizes that might be needed.
Some server tables can alternatively be placed above-the-bar in a non-swappable area. This can be indicated with the SERVNSA and SERVNSSZ parameters.
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.