DSPOPT parameter: Difference between revisions
(Clarified description of DSPOPT=1) |
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<tr class="head"><th>Settings</th><th>Meaning</th></tr> | <tr class="head"><th>Settings</th><th>Meaning</th></tr> | ||
<tr><th align="right"><var>X'01' </var></th> | <tr><th align="right"><var>X'01' </var></th> | ||
<td> | <td>Use MVPG (Move 4K Page) when swapping users to and from CCASERVR. This option applies when using the CCASERVR in Storage feature. With this option enabled, CCASERVR is allocated as one contiguous block of storage, above the bar in 64-bit systems. The size of CCASERVR is calculated by NUSERS*(largest SERVSIZE) and it is logically divided into a collection of 4K pages. | ||
<p> | |||
When users are server swapped to or from CCASERVR, their server slot in CCASERVR might occupy multiple, non-contiguous blocks of 4K pages. This algorithm tends to “front load” CCASERVR, keeping frequently referenced pages at the beginning and results in reduced operating-system paging. This management strategy reduces the number of 4K page moves and keeps the virtual storage allocated to CCASERVR less fragmented and often requires fewer operating-system-page tables. | |||
</p> | |||
<p> | <p> | ||
As of Model 204 version 7.5, this setting is the default. (Previously, X'00' was the default.)</p> | As of Model 204 version 7.5, this setting is the default. (Previously, X'00' was the default.)</p> | ||
Revision as of 22:12, 1 July 2015
Data space options
Summary
- Default value
- X'01'
- Parameter type
- System
- Where set
- On User 0's parameter line
- Related products
- All
- Introduced
- Model 204 V5.1
Description
The bits have the following meanings:
| Settings | Meaning |
|---|---|
| X'01' | Use MVPG (Move 4K Page) when swapping users to and from CCASERVR. This option applies when using the CCASERVR in Storage feature. With this option enabled, CCASERVR is allocated as one contiguous block of storage, above the bar in 64-bit systems. The size of CCASERVR is calculated by NUSERS*(largest SERVSIZE) and it is logically divided into a collection of 4K pages.
When users are server swapped to or from CCASERVR, their server slot in CCASERVR might occupy multiple, non-contiguous blocks of 4K pages. This algorithm tends to “front load” CCASERVR, keeping frequently referenced pages at the beginning and results in reduced operating-system paging. This management strategy reduces the number of 4K page moves and keeps the virtual storage allocated to CCASERVR less fragmented and often requires fewer operating-system-page tables. As of Model 204 version 7.5, this setting is the default. (Previously, X'00' was the default.) |
| X'02' | Put servers in a hiperspace instead of a dataspace.
This setting is applicable only for real dataspaces for non-64-bit systems. |
| X'04' | Use compression when swapping servers. (New in Model 204 version 7.6)
This setting is applicable only for 64-bit in-storage server swapping. When enabled, each table in the server is individually moved based on its usage. |
| X'20' | Put APSY precompiled procedures in hiperspace instead of a dataspace. Hiperspace pages can be in real or expanded storage.
This option is not valid on IBM z/VSE, and it requires that Model 204 be APF-authorized. |
| X'40' | Put APSY precompiled procedures in cache hiperspace instead of a scrolling hiperspace.
Cache hiperspace pages can reside only in expanded storage, so they are sometimes called Also, cache hiperspace pages never result in operating system paging. Pages stolen by the operating system are simply discarded, and Model 204 is responsible for replacing the pages from the copy of the precompiled procedures in CCATEMP. This option is not valid on IBM z/VSE, and it requires that Model 204 be APF-authorized. |
| X'80' | Keep all APSY saved pages in CCATEMP.
Set DSPOPT to X'80' only when TEMPPAGE is 0, and then only in unusual circumstances. |