SCHDOFLZ parameter: Difference between revisions
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<dd>On User 0's parameter line or reset by system manager. | <dd>On User 0's parameter line or reset by system manager. | ||
<dt>Related products | <dt>Related products | ||
<dd> | <dd><var>[[Performance_monitoring_and_tuning#Offloading_Model_204_work_to_zIIP_processors|M204 HPO]]</var> | ||
<dt>Introduced | <dt>Introduced | ||
<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>SCHDOFLZ has no effect if zIIP SRBs are not in effect in an Online (NMPSUBZ | <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>AMPSUBZ</var> set to 1, <var>SCHDOFLZ</var> does not affect any zIIP subtask activation decisions. However, under Model 204 7.5 and 7.6, it would affect non-SRB MP subtask activation and zIIP assistance decisions. Under Model 204 7.7 and later, this aspect of <var>SCHDOFLZ</var> is 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 <var>[[MP/204#Multiprocessing_.28MP.2F204.29|MP]]</var> subtasks. <var>SCHDOFLS</var> controls how aggressively MP subtasks are started to help out zIIP subtasks, as well as how aggressively MP subtasks take work from zIIP subtasks. </p> | |||
<p> | |||
Prior to Model 204 7.7, the minimum allowed value for <var>SCHDOFLZ</var> is 1. Under Model 204 7.7 and later, it is 0, though it is probably a bad idea to set <var>SCHDOFLZ</var> to 0 unless the <var>[[MPDELAYZ parameter|MPDELAYZ]]</var> parameter is set to a non-zero value. | |||
</p> | |||
[[Category:System parameters]] | [[Category:System parameters]] | ||
[[Category:Parameters]] | [[Category:Parameters]] | ||
Latest revision as of 12:05, 24 May 2017
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
- M204 HPO
- 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 AMPSUBZ set to 1, SCHDOFLZ does not affect any zIIP subtask activation decisions. However, under Model 204 7.5 and 7.6, it would affect non-SRB MP subtask activation and zIIP assistance decisions. Under Model 204 7.7 and later, this aspect of SCHDOFLZ is subsumed by SCHDOFLS.
SCHDOFL performs the same function as SCHDOFLZ for non-SRB MP subtasks. SCHDOFLS controls how aggressively MP subtasks are started to help out zIIP subtasks, as well as how aggressively MP subtasks take work from zIIP subtasks.
Prior to Model 204 7.7, the minimum allowed value for SCHDOFLZ is 1. Under Model 204 7.7 and later, it is 0, though it is probably a bad idea to set SCHDOFLZ to 0 unless the MPDELAYZ parameter is set to a non-zero value.