SirMon critical-file-resource monitoring - Revision history

JAL: add link

2017-06-06T20:05:38Z

add link

← Older revision		Revision as of 20:05, 6 June 2017
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	This display is accessed from any file monitor screen in <var class="product">SirMon</var>		This display is accessed from any file monitor screen in <var class="product">SirMon</var>
	(including custom user-defined screens) by pressing the PF2 key		(including custom user-defined screens) by pressing the PF2 key
	with the cursor on a line containing file statistics. The Critical File Resource conflict display is not available in the RKWeb interface.		with the cursor on a line containing file statistics. The Critical File Resource conflict display is not available in the [[RKWeb]] interface.

	The top section of the CFRS screen displays a variety of file-related		The top section of the CFRS screen displays a variety of file-related

JAL: mention RKWeb equivalents

2017-05-16T19:09:27Z

mention RKWeb equivalents

← Older revision		Revision as of 19:09, 16 May 2017
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	~~<!--Page automatically generated by CMSTOWIK EXEC and will be~~
	automatically replaced -- any manual edits will be lost.
	~~You've been warned. .. (Page built by JAL at the SIRIUS VM; file: FUNPGNEW SYSUT2) -->~~
	~~<!-- Page name: SirMon critical-file-resource monitoring-->~~
	==Model 204 critical file resources==		==Model 204 critical file resources==
	<var class="product">Model 204</var> defines four "critical file resources," which are used to serialize access to important file structures.		<var class="product">Model 204</var> defines four "critical file resources," which are used to serialize access to important file structures.
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	==SirMon monitoring of critical file resources==		==SirMon monitoring of critical file resources==
	<var class="product">SirMon</var> supplies you with a variety of statistics for		<var class="product">SirMon</var> supplies you with a variety of statistics for viewing queues and conflicts that have formed against critical file
	viewing queues and conflicts that have formed against critical file
	resources, and it supplies a special screen to help monitor critical		resources, and it supplies a special screen to help monitor critical
	file resource conflicts while they are happening:		file resource conflicts while they are happening:
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	This display is accessed from any file monitor screen in <var class="product">SirMon</var>		This display is accessed from any file monitor screen in <var class="product">SirMon</var>
	(including custom user-defined screens) by pressing the PF2 key		(including custom user-defined screens) by pressing the PF2 key
	with the cursor on a line containing file statistics.		with the cursor on a line containing file statistics. The Critical File Resource conflict display is not available in the RKWeb interface.

	The top section of the CFRS screen displays a variety of file-related		The top section of the CFRS screen displays a variety of file-related
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	waiting) and PNAME (the procedure being run by the user) are displayed for each user.		waiting) and PNAME (the procedure being run by the user) are displayed for each user.

			Critical file resource conflicts and enqueuing problems are always a
			second-order effect indicating some other bottleneck.
			For instance, long queues of users or high numbers of conflicts on the resource called <code>INDEX</code> might point to an inefficient [[SOUL]] program that is unnecessarily locking up a file's index pages.

			<p class="note"><b>Note:</b> Users waiting in queues, but not holding enqueues on critical file resources, are not displayed here. They can be seen in User Monitor displays showing WAITTYP and WAITTIM. </p>

			===Waiting users===
			<b>WT</b> is a numeric code used by <var class="product">Model 204</var> to indicate the type of wait a user is experiencing.
			WAITTYPEs 24 and 25 indicate a wait on a critical file resource. <var class="product">SirMon</var> displays the <b>WT</b> statistic as a two-digit code, ordinarily the numeric wait type. However, codes 24 and 25 are displayed as two alphabetic characters:
	<ul>		<ul>
	<li>WT is a numeric code used by <var class="product">Model 204</var> to indicate the type of wait a user is experiencing. WAITTYPEs 24 and 25 indicate a wait on a critical file resource. <var class="product">SirMon</var> displays the WT statistic as a two-digit code, ordinarily the numeric wait type. However, codes 24 and 25 are displayed as two alphabetic characters.		<li>The first character indicates the particular critical file resource
	The first character indicates the particular critical file resource
	being waited on, as follows:		being waited on, as follows:

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	<tr><th>R</th>		<tr><th>R</th>
	<td>RECENQ</td></tr>		<td>RECENQ</td></tr>
	</table>		</table></li>
	The second character indicates the strength of enqueue being sought:
			<li>The second character indicates the strength of enqueue being sought:

	<table class="thJustBold">		<table class="thJustBold">
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	<tr><th>S</th>		<tr><th>S</th>
	<td>Share</td></tr>		<td>Share</td></tr>
	</table>		</table></li>
			</ul>

	<p>		<p>
	For example, a WT value of <code>DS</code> indicates that the		For example, a <b>WT</b> value of <code>DS</code> indicates that the
	DIRECT resource is required in share mode, while a WT value		DIRECT resource is required in share mode, while a WT value
	of <code>RE</code> indicates that the RECENQ resource is required in		of <code>RE</code> indicates that the RECENQ resource is required in
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	If a user is waiting for a critical file resource, the user that currently		If a user is waiting for a critical file resource, the user that currently
	holds the requested critical file resource should be investigated.		holds the requested critical file resource should be investigated.
	For example, if a user has a WT value of <code>IS</code>, you should		For example, if a user has a <b>WT</b> value of <code>IS</code>, you should
	find another user holding the <code>INDEX</code> resource in exclusive mode.		find another user holding the <code>INDEX</code> resource in exclusive mode.
	Whatever this second user is waiting upon is generally the root cause of		Whatever this second user is waiting upon is generally the root cause of
	the first user's <code>IS</code> wait.</p>		the first user's <code>IS</code> wait.</p>
	~~</ul>~~

			===Related statistics===
	Along with statistics displayed on this special critical file resource		Along with statistics displayed on this special critical file resource
	screen, there are quite a number of other statistics, at the System,		screen, there are quite a number of other statistics, at the System,
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	resource waits.</li>		resource waits.</li>
	</ul>		</ul>

	~~Critical file resource conflicts and enqueuing problems are always a~~
	~~second-order effect indicating some other bottleneck.~~
	For instance, long queues of users or high numbers of conflicts on the resource called <code>INDEX</code> might point to an inefficient [[SOUL]] program that is unnecessarily locking up a file's index pages.

	<p class="note"><b>Note:</b> Users waiting in queues, but not holding enqueues on critical file resources, are not displayed here. They can be seen in User Monitor displays showing WAITTYP and WAITTIM. </p>

	==See also==		==See also==

JAL: misc formatting

2015-11-03T22:21:37Z

misc formatting

← Older revision		Revision as of 22:21, 3 November 2015
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	file resource conflicts while they are happening:		file resource conflicts while they are happening:

	<p class="caption" style="width:475px">Critical File Resource ~~Conflict~~ display</p>		<p class="caption" style="width:475px">Critical File Resource conflict display</p>
	<p class="figure">[[File:SmonCFRSconf.png\|475px]]</p>		<p class="figure">[[File:SmonCFRSconf.png\|475px]]</p>

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	of enqueue each is holding.		of enqueue each is holding.
	In addition, WT (WAITTYPE), WTIME (the length of time the user has been		In addition, WT (WAITTYPE), WTIME (the length of time the user has been
	waiting) and PNAME (the procedure being run by the user) is displayed for each user.		waiting) and PNAME (the procedure being run by the user) are displayed for each user.

	<ul>		<ul>
	<li>WT is a numeric code used by <var class="product">Model 204</var> to indicate the type of wait a user is experiencing. WAITTYPEs 24 and 25 indicate a wait on a critical file resource. <var class="product">SirMon</var> displays the WT statistic as a two-digit code, ordinarily the numeric wait type.		<li>WT is a numeric code used by <var class="product">Model 204</var> to indicate the type of wait a user is experiencing. WAITTYPEs 24 and 25 indicate a wait on a critical file resource. <var class="product">SirMon</var> displays the WT statistic as a two-digit code, ordinarily the numeric wait type. However, codes 24 and 25 are displayed as two alphabetic characters.
	However, codes 24 and 25 are displayed as two alphabetic characters.
	The first character indicates the particular critical file resource		The first character indicates the particular critical file resource
	being waited on, as follows:		being waited on, as follows:
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	Critical file resource conflicts and enqueuing problems are always a		Critical file resource conflicts and enqueuing problems are always a
	second-order effect indicating some other bottleneck.		second-order effect indicating some other bottleneck.
	For instance, long queues of users or high numbers of conflicts on the resource		For instance, long queues of users or high numbers of conflicts on the resource called <code>INDEX</code> might point to an inefficient [[SOUL]] program that is unnecessarily locking up a file's index pages.
	called INDEX might point to an inefficient [[SOUL]] program that
	is unnecessarily locking up a file's index pages.

	<p class="note"><b>Note:</b> Users waiting in queues, but not holding enqueues on		<p class="note"><b>Note:</b> Users waiting in queues, but not holding enqueues on critical file resources, are not displayed here. They can be seen in User Monitor displays showing WAITTYP and WAITTIM. </p>
	critical file resources, are not displayed here. They can be seen in User Monitor displays showing WAITTYP and WAITTIM. </p>

	==See also==		==See also==

JAL: reduce size of graphic

2015-09-10T23:09:58Z

reduce size of graphic

← Older revision		Revision as of 23:09, 10 September 2015
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	file resource conflicts while they are happening:		file resource conflicts while they are happening:

	<p class="caption" style="width:~~500px~~">Critical File Resource Conflict display</p>		<p class="caption" style="width:475px">Critical File Resource Conflict display</p>
	<p class="figure">[[File:SmonCFRSconf.png\|~~500px~~]]</p>		<p class="figure">[[File:SmonCFRSconf.png\|475px]]</p>

	This display is accessed from any file monitor screen in <var class="product">SirMon</var>		This display is accessed from any file monitor screen in <var class="product">SirMon</var>

Admin: 1 revision: SirMon pages

2015-09-10T22:05:21Z

1 revision: SirMon pages

← Older revision	Revision as of 22:05, 10 September 2015
(No difference)

JAL: add graphic

2015-09-10T15:59:43Z

add graphic

New page

==Model 204 critical file resources==
<var class="product">Model 204</var> defines four "critical file resources," which are used to serialize access to important file structures.
The names of these resources and the resources that they control are:

<table class="thJustBold">
<tr><th>DIRECT</th>
<td>Controls access to Table B records.</td></tr>

<tr><th>INDEX</th>
<td>Controls access to index structures in both Table C and Table D.</td></tr>

<tr><th>EXISTS</th>
<td>Controls access to the existence bit-map.</td></tr>

<tr><th>RECENQ</th>
<td>Controls access to record enqueueing data structures representing found sets and record lists.</td></tr>
</table>

A set of internal rules govern access to critical file resources:
A thread must hold a resource in SHR mode to examine the associated file structure.
A thread must hold a resource in EXC mode to modify the associated file structure.
Multiple threads may hold a resource in SHR mode but only a single thread
may hold a resource in EXC mode.
A resource may not be held in SHR and EXC modes simultaneously.
A thread may hold any number of resources for a single
file but will never hold resources in more than one file at a time.

When a thread is prevented by the above rules from obtaining a required
resource, the thread must wait until the resource becomes available:
this is called a critical file resource "conflict."
In this situation, the requesting thread is placed on a queue of users
waiting for the resource.
The thread is said to be "enqueued" on the critical file resource.

==SirMon monitoring of critical file resources==
<var class="product">SirMon</var> supplies you with a variety of statistics for
viewing queues and conflicts that have formed against critical file
resources, and it supplies a special screen to help monitor critical
file resource conflicts while they are happening:

<p class="caption" style="width:500px">Critical File Resource Conflict display</p>
<p class="figure">[[File:SmonCFRSconf.png|500px]]</p>

This display is accessed from any file monitor screen in <var class="product">SirMon</var>
(including custom user-defined screens) by pressing the PF2 key
with the cursor on a line containing file statistics.

The top section of the CFRS screen displays a variety of file-related
statistics (described in [[Critical File Resource statistics displayed in SirMon]]) showing the rate of
conflicts and the current length of the queue of users waiting for each
of the four critical file resources.
Disk reads and writes (DKRD/DKWR) are also displayed, as
are the total number of the file's pages currently in buffers (BUFPAGE)
and the total number of users queued, waiting for any critical file
resource for the file.

The lower portion of the screen displays users who currently hold
enqueues on critical file resources for the selected file, and the type
of enqueue each is holding.
In addition, WT (WAITTYPE), WTIME (the length of time the user has been
waiting) and PNAME (the procedure being run by the user) is displayed for each user.

<ul>
<li>WT is a numeric code used by <var class="product">Model 204</var> to indicate the type of wait a user is experiencing. WAITTYPEs 24 and 25 indicate a wait on a critical file resource. <var class="product">SirMon</var> displays the WT statistic as a two-digit code, ordinarily the numeric wait type.
However, codes 24 and 25 are displayed as two alphabetic characters.
The first character indicates the particular critical file resource
being waited on, as follows:

<table class="thJustBold">
<tr><th>D</th>
<td>DIRECT</td></tr>

<tr><th>I</th>
<td>INDEX</td></tr>

<tr><th>E</th>
<td>EXISTS</td></tr>

<tr><th>R</th>
<td>RECENQ</td></tr>
</table>
The second character indicates the strength of enqueue being sought:

<table class="thJustBold">
<tr><th>E</th>
<td>Exclusive</td></tr>

<tr><th>S</th>
<td>Share</td></tr>
</table>
<p>
For example, a WT value of <code>DS</code> indicates that the
DIRECT resource is required in share mode, while a WT value
of <code>RE</code> indicates that the RECENQ resource is required in
exclusive mode. This translation of WAITTYPEs is vital in determining the root cause of a critical file resource enqueuing problem.</p>
<p>
If a user is waiting for a critical file resource, the user that currently
holds the requested critical file resource should be investigated.
For example, if a user has a WT value of <code>IS</code>, you should
find another user holding the <code>INDEX</code> resource in exclusive mode.
Whatever this second user is waiting upon is generally the root cause of
the first user's <code>IS</code> wait.</p>
</ul>

Along with statistics displayed on this special critical file resource
screen, there are quite a number of other statistics, at the System,
File, and User levels, that are related to critical file resource monitoring.
An understanding of how these statistics relate to critical file resources
is key to effectively identifying and fixing related problems.

<ul>
<li>CFRCONF and CFRQUEU exist on system and file levels.
These statistics are the sums of the resource type queue lengths and number
of conflicts occurring.
<p>
CFRCONF is provided to flag situations where a critical file resource is being
obtained and released relatively frequently, often producing short lived conflicts. This situation could produce unnecessarily high CPU utilization because of extra scheduler overhead. Two updating "batch" type jobs could produce this kind of problem.</p>
<p>
CFRQUEU is provided to flag situations where an application
holds a critical file resource for excessive periods of time producing
long queues of users waiting for the resource. </p>
<p>
CFRCONF exists on the user level, and at this level it indicates the
number of times a user thread has had to wait on a critical file resource.
Also on the user level, CFRCWTT indicates the amount of time
a user has waited on critical file resources. </p></li>

<li>The WAITFIL statistic indicates the name of the file being waited on,
and is reported for both critical file resource waits and disk I/O.</li>

<li>The WAITCFR statistic indicates the abbreviated name of the critical
file resource being waited on, and is only reported for critical file
resource waits.</li>
</ul>

Critical file resource conflicts and enqueuing problems are always a
second-order effect indicating some other bottleneck.
For instance, long queues of users or high numbers of conflicts on the resource
called INDEX might point to an inefficient [[SOUL]] program that
is unnecessarily locking up a file's index pages.

<p class="note"><b>Note:</b> Users waiting in queues, but not holding enqueues on
critical file resources, are not displayed here. They can be seen in User Monitor displays showing WAITTYP and WAITTIM. </p>

==See also==
{{Template:SirMon topic list}}

[[Category: SirMon]]