SCHDOPT1 parameter: Difference between revisions

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{{Template:SCHDOPT1 parameter subtitle}}
Flags that, in addition to the [[SCHDOPT parameter]], allow one to tune scheduler behavior. <var>SCHDOPT1</var> is a parameter where the following bits control 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.  
<td>Journal and checkpoint I/O cannot be performed on a zIIP subtask; that I/O operation must start on an MP subtask or on the maintask.  When this parameter is set to X’01’, a user running on a zIIP subtask who needs to write to the CCAJRNL/JLOG or CHKPOINT data set, will be switched to the maintask, not an MP subtask, and the I/O operation will start on the maintask.  Waits for an MP subtask to become available on a busy system can be significantly longer than waits for the maintask to become available.  There is also more overhead to switch to an MP subtask than to the maintask. Consequently, this feature reduces wait times to start an I/O to the CCAJRNL/JLOG and CHKPOINT data sets when a unit of work is running on a zIIP subtask.  
<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>
 
For more information about zIIP processing, refer to the descriptions for the[[AMPSUBZ parameter]], [[MPDELAYZ parameter]], [[NMPSUBZ parameter]], [[SCHDOFLS parameter]] and [[SCHDOFLZ parameter]].
</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 20:57, 15 February 2022

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

SettingMeaning
X'01' Journal and checkpoint I/O cannot be performed on a zIIP subtask; that I/O operation must start on an MP subtask or on the maintask. When this parameter is set to X’01’, a user running on a zIIP subtask who needs to write to the CCAJRNL/JLOG or CHKPOINT data set, will be switched to the maintask, not an MP subtask, and the I/O operation will start on the maintask. Waits for an MP subtask to become available on a busy system can be significantly longer than waits for the maintask to become available. There is also more overhead to switch to an MP subtask than to the maintask. Consequently, this feature reduces wait times to start an I/O to the CCAJRNL/JLOG and CHKPOINT data sets when a unit of work is running on a zIIP subtask.

For more information about zIIP processing, refer to the descriptions for theAMPSUBZ parameter, MPDELAYZ parameter, NMPSUBZ parameter, SCHDOFLS parameter and SCHDOFLZ parameter.

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