CFROPTS parameter: Difference between revisions
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==Description== | ==Description== | ||
<p>The CFROPTS parameter can affect the handling of critical file resource enqueuing conflicts. The parameter contains bit settings with the following possible values:</p> | <p> | ||
The <var>CFROPTS</var> parameter can affect the handling of critical file resource enqueuing conflicts. The parameter contains bit settings with the following possible values:</p> | |||
<table> | <table> | ||
<tr><th | <tr class="head"><th>Setting </th><th>Meaning</th></tr> | ||
</th><th | <tr><th><var>X'01'</var></th> | ||
<td>Indicates that strict fair share enqueuing will be used. This prevents one thread from sneaking ahead of another in obtaining a critical file resource lock because it happens to be running before a thread that had been waiting for the lock before it. While this "sneaking ahead" can reduce CFR lock waits and associated swapping at low loads (because the sneaking thread might finish before the waiting one ever runs), it can increase waits and thrashing at high loads, and it can cause abysmal response times for updating threads. | |||
</th></tr> | <p> | ||
<tr><th | The increased server swapping when <var>CFROPTS</var> X'01' is not set is caused by a variant of the [http://en.wikipedia.org/wiki/Thundering_herd_problem thundering herd problem].</p></td></tr> | ||
</var></th><td | |||
</td></tr> | |||
</table> | </table> | ||
[[Category:System parameters]] | [[Category:System parameters]] | ||
[[Category:Parameters]] | [[Category:Parameters]] | ||
Revision as of 20:45, 18 March 2015
Audit options
Summary
- Default value
- X'00'
- Parameter type
- System
- Where set
- On User 0's parameter line or reset by system manager
- Related products
- All
- Introduced
- Model 204 V7.6
Description
The CFROPTS parameter can affect the handling of critical file resource enqueuing conflicts. The parameter contains bit settings with the following possible values:
| Setting | Meaning |
|---|---|
| X'01' | Indicates that strict fair share enqueuing will be used. This prevents one thread from sneaking ahead of another in obtaining a critical file resource lock because it happens to be running before a thread that had been waiting for the lock before it. While this "sneaking ahead" can reduce CFR lock waits and associated swapping at low loads (because the sneaking thread might finish before the waiting one ever runs), it can increase waits and thrashing at high loads, and it can cause abysmal response times for updating threads.
The increased server swapping when CFROPTS X'01' is not set is caused by a variant of the thundering herd problem. |