SCHDOFLZ parameter: Difference between revisions
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<dd><var class="product">Model 204 V7.4</var> | <dd><var class="product">Model 204 V7.4</var> | ||
</dl> | </dl> | ||
==Description== | ==Description== | ||
<p> | <p> | ||
<p>On a z/OS system, <var class="product">Model 204</var> zIIP support enables you to offload <var class="product">Model 204</var> work from regular processors to zIIP processors.</p> | This parameter applies to z/OS only.</p> | ||
<p>SCHDOFLZ specifies the target number of threads on the zIIP offload queue per active task. Setting this parameter makes the <var class="product">Model 204</var> zIIP subtask scheduler more responsive to instantaneous increases in load.</p> | <p> | ||
<p>The default value | On a z/OS system, <var class="product">Model 204</var> zIIP support enables you to offload <var class="product">Model 204</var> work from regular processors to zIIP processors.</p> | ||
<p><var>SCHDOFLZ</var> has no effect if zIIP SRBs are not in effect in an Online (<var>NMPSUBZ</var> | <p> | ||
<p> | <var>SCHDOFLZ</var> specifies the target number of threads on the zIIP offload queue per active task. Setting this parameter makes the <var class="product">Model 204</var> zIIP subtask scheduler more responsive to instantaneous increases in load.</p> | ||
<p> | |||
The default value, 2, means that if there are more than twice as many units of zIIP offloadable work waiting to be processed in a zIIP subtask as there are active subtasks, and fewer than <var>AMPSUBZ</var> subtasks are currently running, another zIIP offload subtask is activated. </p> | |||
<p> | |||
<var>SCHDOFLZ</var> has no effect if either of these is true: </p> | |||
<ul> | |||
<li>zIIP SRBs are not in effect in an Online (<var>[[NMPSUBZ parameter|NMPSUBZ]]</var> is 0).</li> | |||
<li>The number of active SRBs (<var>[[AMPSUBZ parameter|AMPSUBZ]]</var>) is set to 0. </li> | |||
</ul> | |||
<p> | |||
If <var>AMPSUBZ</var> is 1, a zIIP subtask is activated as soon as there is any offloadable work, and it then runs until there is no more offloadable work for it to process. So with <var>AMPSUB</var>=1, <var>SCHDOFLZ</var> does not affect any zIIP subtask activation decisions. However, under Model 204 7.5 and 7.6, it would affect a non-SRB MP subtask activation and zIIP assistance decisions. Under Model 204 7.7 and later, this aspect of <var>SCHDOFLZ</var> as been subsumed by <var>[[SCHDOFLS parameter|SCHDOFLS]]</var>.</p> | |||
<p> | |||
<var>[[SCHDOFL parameter|SCHDOFL]]</var> performs the same function as <var>SCHDOFLZ</var> for non-SRB MP subtasks, and <var>[[SCHDOFLS parameter|SCHDOFLS]]</var> controls how aggressively MP subtasks are started to help zIIP subtasks out, as well as how aggressively MP subtasks take work from zIIP subtasks. </p> | |||
[[Category:System parameters]] | [[Category:System parameters]] | ||
[[Category:Parameters]] | [[Category:Parameters]] | ||
Revision as of 16:43, 28 July 2016
Threshold for activating zIIP subtasks
Summary
- Default value
- 2
- Parameter type
- System
- Where set
- On User 0's parameter line or reset by system manager.
- Related products
- All
- Introduced
- Model 204 V7.4
Description
This parameter applies to z/OS only.
On a z/OS system, Model 204 zIIP support enables you to offload Model 204 work from regular processors to zIIP processors.
SCHDOFLZ specifies the target number of threads on the zIIP offload queue per active task. Setting this parameter makes the Model 204 zIIP subtask scheduler more responsive to instantaneous increases in load.
The default value, 2, means that if there are more than twice as many units of zIIP offloadable work waiting to be processed in a zIIP subtask as there are active subtasks, and fewer than AMPSUBZ subtasks are currently running, another zIIP offload subtask is activated.
SCHDOFLZ has no effect if either of these is true:
- zIIP SRBs are not in effect in an Online (NMPSUBZ is 0).
- The number of active SRBs (AMPSUBZ) is set to 0.
If AMPSUBZ is 1, a zIIP subtask is activated as soon as there is any offloadable work, and it then runs until there is no more offloadable work for it to process. So with AMPSUB=1, SCHDOFLZ does not affect any zIIP subtask activation decisions. However, under Model 204 7.5 and 7.6, it would affect a non-SRB MP subtask activation and zIIP assistance decisions. Under Model 204 7.7 and later, this aspect of SCHDOFLZ as been subsumed by SCHDOFLS.
SCHDOFL performs the same function as SCHDOFLZ for non-SRB MP subtasks, and SCHDOFLS controls how aggressively MP subtasks are started to help zIIP subtasks out, as well as how aggressively MP subtasks take work from zIIP subtasks.