Difference between revisions of "SCHDOPT1 parameter"

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{{Template:SCHDOPT1 parameter subtitle}}
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Flags that, in addition to the [[SCHDOPT parameter]], allows one to tune scheduler behavior. <var>SCHDOPT1</var> is a parameter where the following bits control a certain aspects of scheduler behavior:
  
==Summary==
 
<dl>
 
<dt>Default value
 
<dd>0
 
<dt>Parameter type
 
<dd>System
 
<dt>Where set
 
<dd>On User 0's parameter line or reset by system manager.
 
<dt>Related products
 
<dd><var>[[MP/204#Multiprocessing_.28MP.2F204.29|MP/204]]</var> and <var>[[Performance_monitoring_and_tuning#Offloading_Model_204_work_to_zIIP_processors|M204 HPO]]</var>
 
<dt>Introduced
 
<dd><var class="product">Model 204 V7.4</var>
 
</dl>
 
 
==Description==
 
Allows an MP subtask to handle [[Creating server data sets (CCASERVR)#Overview|server swapping]], if applicable.
 
 
<var>SCHDOPT1</var> is useful when a [[Performance monitoring and tuning#Offloading Model 204 work to zIIP processors|zIIP processor]] is handling server swapping and needs help from an MP subtask.
 
 
Setting X'01' is relevant only to sites running MP/204.
 
 
<table>
 
<table>
 
<tr class="head"><th>Setting</th><th>Meaning</th></tr>
 
<tr class="head"><th>Setting</th><th>Meaning</th></tr>
 
<tr><th align="right"><var>X'01'</var></th>
 
<tr><th align="right"><var>X'01'</var></th>
<td>(MP/204 only) Allows an MP subtask to handle server swapping if the subtask has nothing else to do.
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<td>Indicates that threads that are running on a zIIP-capable SRB and need to do journal I/O do not "bounce" to a non-zIIP subtask to do the journal or checkpoint I/O but simply perform it on the maintask. Since generally very little processing is involved in doing journal or checkpoint I/O, sending a thread to an MP task to do the I/O only increases latency and saves no maintask processing overhead.
<p><b>Note:</b> As of version 7.6 of Model&nbsp;204, this setting is disabled (has no effect), because the behavior it invoked is automatically on in those versions.</p></td></tr>
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This setting also prevents a thread running on a non-zIIP task and that has to wait for another thread doing journal or checkpoint I/O before doing the same from bouncing between maintask and subtask to do the I/O &ndash; when the X'01' bit is set, the I/O will be performed on the maintask, again reducing I/O latency. This bit has a much more significant effect if zIIP subtasks are in use. For more information about zIIP processing, refer to the [[SCHDOPT parameter]] and [[AMPSUBZ parameter]] descriptions.
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</td></tr>
 
</table>
 
</table>
 
For more information about zIIP processing, refer to the <var>[[SCHDOPT parameter|SCHDOPT]]</var> parameter description.
 
 
[[Category:System parameters]]
 
[[Category:Parameters]]
 

Latest revision as of 14:35, 21 June 2020

Flags that, in addition to the SCHDOPT parameter, allows one to tune scheduler behavior. SCHDOPT1 is a parameter where the following bits control a certain aspects of scheduler behavior:

SettingMeaning
X'01' Indicates that threads that are running on a zIIP-capable SRB and need to do journal I/O do not "bounce" to a non-zIIP subtask to do the journal or checkpoint I/O but simply perform it on the maintask. Since generally very little processing is involved in doing journal or checkpoint I/O, sending a thread to an MP task to do the I/O only increases latency and saves no maintask processing overhead.

This setting also prevents a thread running on a non-zIIP task and that has to wait for another thread doing journal or checkpoint I/O before doing the same from bouncing between maintask and subtask to do the I/O – when the X'01' bit is set, the I/O will be performed on the maintask, again reducing I/O latency. This bit has a much more significant effect if zIIP subtasks are in use. For more information about zIIP processing, refer to the SCHDOPT parameter and AMPSUBZ parameter descriptions.