In-memory files - Revision history

JAL: minor cleanup

2015-06-03T20:32:36Z

minor cleanup

← Older revision		Revision as of 20:32, 3 June 2015
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	<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>		<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>
	<blockquote class="note"><b>Note:</b> You <strong>cannot</strong> create in-memory files that are part of a multi-dataset file, such as the following:		<blockquote class="note"><b>Note:</b> You <strong>cannot</strong> create in-memory files that are part of a multi-dataset file, such as the following:
	<p class="code">CREATE FILE filename FROM filenam1,filenam2		<p class="code">CREATE FILE <i>filename</i> FROM <i>filenam1</i>, <i>filenam2</i>
	</p>		</p>
	</blockquote>		</blockquote>

	[[Category:Model 204 files]]		[[Category:Model 204 files]]

JAL: misc formatting

2015-06-03T20:28:09Z

misc formatting

← Older revision		Revision as of 20:28, 3 June 2015
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	</ul>		</ul>

	All pages for an in-memory file reside in and use system memory (above the bar) while still taking advantage of the structure and capabilities of a Model 204 file.		All pages for an in-memory file reside in and use system memory (above the bar) while still taking advantage of the structure and capabilities of a Model 204 file.

	Using an in-memory file reduces CPU time processing, such as <var>COMMIT</var> statements and file page loading and swapping, as the file pages remain in storage even after the last physical file close. All in-memory file pages are shared among all users via the buffer pool, like any other Model 204 file.		Using an in-memory file reduces CPU time processing, such as <var>COMMIT</var> statements and file page loading and swapping, as the file pages remain in storage even after the last physical file close. All in-memory file pages are shared among all users via the buffer pool, like any other Model 204 file.

	===Opening and closing in-memory files===		===Opening and closing in-memory files===
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	===Restoring an in-memory file===		===Restoring an in-memory file===
	<p>		<p>
	When you create an in-memory file, the default FRCVOPT is X'24', which means that this file does not participate in journal and checkpoint logging.</p>		When you create an in-memory file, the default <var>FRCVOPT</var> is X'24', which means that this file does not participate in journal and checkpoint logging.</p>

	<p>However, remember that restoring an in-memory file with RESTORE from a backup will copy the FRCVOPT from that backup copy into the in-memory file, thus overriding the default. In-memory files are also created with FOPT=0, which is TBO enabled, and TBO is supported. REGENERATE is also supported. RESTART recovery is not supported.</p>		<p>However, remember that restoring an in-memory file with <var>RESTORE</var> from a backup will copy the <var>FRCVOPT</var> from that backup copy into the in-memory file, thus overriding the default. In-memory files are also created with <code>FOPT=0</code>, which is TBO enabled, and TBO is supported. <var>REGENERATE</var> is also supported. <var>RESTART</var> recovery is not supported.</p>

	<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>		<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>
	<p class="note"><b>Note:</b> You <strong>cannot</strong> create in-memory files that are part of a multi-dataset file, such as the following:		<blockquote class="note"><b>Note:</b> You <strong>cannot</strong> create in-memory files that are part of a multi-dataset file, such as the following:
	~~<br/></p>~~
	<p class="code">CREATE FILE filename FROM filenam1,filenam2		<p class="code">CREATE FILE filename FROM filenam1,filenam2
	</p>		</p>
			</blockquote>

	[[Category:Model 204 files]]		[[Category:Model 204 files]]

Alex at 03:22, 25 February 2015

2015-02-25T03:22:38Z

← Older revision		Revision as of 03:22, 25 February 2015
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	<p class="note"><b>Note:</b> In-memory files are not supported on z/VSE systems.</p>		<p class="note"><b>Note:</b> In-memory files are not supported on z/VSE systems.</p>

	If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the <var>MEMORY PAGES</var> keywords in ~~either the <var>[[DEFINE DATASET command\|DEFINE DATASET]]</var> command or~~ the <var>[[ALLOCATE command\|ALLOCATE]]</var> command.		If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the <var>MEMORY PAGES</var> keywords in the <var>[[ALLOCATE command\|ALLOCATE]]</var> command.

	In-memory files let you use system memory and take advantage of the structure and capabilities of a Model 204 file. The most important capability is that the file pages are shared among all users, and file updates can be backed out on a transaction back out. Most system memory access requires no extra movement of data to or from the buffer pools and does not affect buffer pool performance.		In-memory files let you use system memory and take advantage of the structure and capabilities of a Model 204 file. The most important capability is that the file pages are shared among all users, and file updates can be backed out on a transaction back out. Most system memory access requires no extra movement of data to or from the buffer pools and does not affect buffer pool performance.

DmeWiccan: Automatically generated page update

2014-05-09T22:44:26Z

Automatically generated page update

← Older revision		Revision as of 22:44, 9 May 2014
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	</p>		</p>

	[[Category: ~~File management~~]]		[[Category:Model 204 files]]

ELowell: /* Restoring an in-memory file */

2014-03-04T20:18:30Z

Restoring an in-memory file

← Older revision		Revision as of 20:18, 4 March 2014
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	When you create an in-memory file, the default FRCVOPT is X'24', which means that this file does not participate in journal and checkpoint logging.</p>		When you create an in-memory file, the default FRCVOPT is X'24', which means that this file does not participate in journal and checkpoint logging.</p>

	<p>However, remember that restoring an in-memory file with RESTORE from a backup will copy the FRCVOPT from that backup copy into the in-memory file, thus overriding the default. In-memory files are also created with FOPT=0, which is TBO enabled, and TBO is supported. REGENERATE is also supported. RESTART recovery is not supported.		<p>However, remember that restoring an in-memory file with RESTORE from a backup will copy the FRCVOPT from that backup copy into the in-memory file, thus overriding the default. In-memory files are also created with FOPT=0, which is TBO enabled, and TBO is supported. REGENERATE is also supported. RESTART recovery is not supported.</p>

	~~Given these caveats, if you want to provide for both REGENERATE recovery and TBO, the best parameter settings for in-memory files are FRCVOPT=X’20’ and FOPT=0~~.</p>

	<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>		<p>The [[DUMP command]] and [[RESTORE command]] can process in-memory files.</p>

ELowell: /* Freeing an in-memory file */

2014-03-04T20:12:02Z

Freeing an in-memory file

@@ Line 36: / Line 36: @@
 ===Freeing an in-memory file===
 When an in-memory file is no longer required, you can free it with the <var>[[FREE command|FREE]]</var> command.
 [[Category: File management]]

JAL: minor cleanup

2014-02-22T01:58:52Z

minor cleanup

← Older revision		Revision as of 01:58, 22 February 2014
Line 3:		Line 3:
	<p class="note"><b>Note:</b> In-memory files are not supported on z/VSE systems.</p>		<p class="note"><b>Note:</b> In-memory files are not supported on z/VSE systems.</p>

	If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the MEMORY PAGES keywords in either the [[DEFINE DATASET command]] or [[ALLOCATE command]].		If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the <var>MEMORY PAGES</var> keywords in either the <var>[[DEFINE DATASET command\|DEFINE DATASET]]</var> command or the <var>[[ALLOCATE command\|ALLOCATE]]</var> command.

	In-memory files let you use system memory and take advantage of the structure and capabilities of a Model 204 file. The most important capability is that the file pages are shared among all users and file updates can be backed out on a transaction back out. Most system memory access requires no extra movement of data to or from the buffer pools and does not affect buffer pool performance.		In-memory files let you use system memory and take advantage of the structure and capabilities of a Model 204 file. The most important capability is that the file pages are shared among all users, and file updates can be backed out on a transaction back out. Most system memory access requires no extra movement of data to or from the buffer pools and does not affect buffer pool performance.

	The following scenarios show how you might use in-memory files:		The following scenarios show how you might use in-memory files:
Line 11:		Line 11:
	<ul>		<ul>
	<li>		<li>
	You have a WORK file that applications use.		You have a <code>WORK</code> file that applications use.
	<br>		<p>
	If this is an in-memory file, all file read (DKRD) and write (DKWR) operations merely move pages from the in-memory file to and from the buffer pool for processing just like any other file, but there is no physical disk I/O. Any updated pages will be moved (DKWR) back to the in-memory file, but that also avoids physical disk I/O.		If this is an in-memory file, all file read (DKRD) and write (DKWR) operations merely move pages from the in-memory file to and from the buffer pool for processing just like any other file, but there is no physical disk I/O. Any updated pages will be moved (DKWR) back to the in-memory file, but that also avoids physical disk I/O. </p></li>
	</li>

	<li>		<li>You have a file that gets an extremely high number of updates.
	You have a file that gets an extremely high number of updates.		<p>
	<br>		This file can be allocated as an in-memory file and restored from a backup copy. Then it can be used by any update processes needed, and when complete, the file can be closed by all users and then dumped to the backup data set. </p></li>
	This file can be allocated as an in-memory file and restored from a backup copy. Then it can be used by any update processes needed, and when complete, the file can be closed by all users and then dumped to the backup data set.
	</li>
	</ul>		</ul>

	All pages for an in-memory file reside in and use system memory (above the bar) while still taking advantage of the structure and capabilities of a Model 204 file.		All pages for an in-memory file reside in and use system memory (above the bar) while still taking advantage of the structure and capabilities of a Model 204 file.

	Using an in-memory file reduces CPU time processing, such as COMMIT statements and file page loading and swapping, as the file pages remain in storage even after the last physical file close. All in-memory file pages are shared among all users via the buffer pool, like any other Model 204 file.		Using an in-memory file reduces CPU time processing, such as <var>COMMIT</var> statements and file page loading and swapping, as the file pages remain in storage even after the last physical file close. All in-memory file pages are shared among all users via the buffer pool, like any other Model 204 file.

	===Opening and closing in-memory files===		===Opening and closing in-memory files===
	You must define the data set with the MEMORY and PAGES keywords, then		You must define the data set with the <var>MEMORY</var> and <var>PAGES</var> keywords, then
	create it, open it, and initialize it. Afterward, you can use the file as you would		create it, open it, and initialize it. Afterward, you can use the file as you would
	any other Model 204 file.		any other Model 204 file.
	<ul>		<ul>
	<li>The FPL page enqueue list is maintained for in-memory files.</li>		<li>The FPL page enqueue list is maintained for in-memory files.</li>
	<li>The system enqueues used to protect FPL page updates are not used for		<li>The system enqueues used to protect FPL page updates are <i>not</i> used for
	in-memory files.</li>		in-memory files.</li>
	</ul>		</ul>

	===Freeing an in-memory file===		===Freeing an in-memory file===
	When an in-memory file is no longer required, you can free it with the [[FREE command]].		When an in-memory file is no longer required, you can free it with the <var>[[FREE command\|FREE]]</var> command.

	[[Category: File management]]		[[Category: File management]]

ELowell at 00:08, 2 July 2013

2013-07-02T00:08:30Z

← Older revision		Revision as of 00:08, 2 July 2013
Line 1:		Line 1:
	You can create temporary in-memory Model 204 files~~, which~~ incur less CPU overhead and none of the I/O associated with permanent Model 204 files.		You can create temporary in-memory Model 204 files to reduce the CPU time used for physical commits and reloading pages from files that have been physically closed while you are working. In-memory Model 204 files incur less CPU overhead and none of the I/O associated with permanent Model 204 files.

	<p class="note"><b>Note:</b> ~~This feature is~~ not supported on z/VSE systems.</p>		<p class="note"><b>Note:</b> In-memory files are not supported on z/VSE systems.</p>

	If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the MEMORY PAGES keywords in either the [[DEFINE DATASET command]] or [[ALLOCATE command]].		If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the MEMORY PAGES keywords in either the [[DEFINE DATASET command]] or [[ALLOCATE command]].

			In-memory files let you use system memory and take advantage of the structure and capabilities of a Model 204 file. The most important capability is that the file pages are shared among all users and file updates can be backed out on a transaction back out. Most system memory access requires no extra movement of data to or from the buffer pools and does not affect buffer pool performance.

	The following scenarios show how you might use in-memory files:		The following scenarios show how you might use in-memory files:

ELowell: Created page with "You can create temporary in-memory Model 204 files, which incur less CPU overhead and none of the I/O associated with permanent Model 204 files.
Note: ..."

2013-06-21T18:28:18Z

Created page with "You can create temporary in-memory Model 204 files, which incur less CPU overhead and none of the I/O associated with permanent Model 204 files. Note: ..."

New page

You can create temporary in-memory Model 204 files, which incur less CPU overhead and none of the I/O associated with permanent Model 204 files.

Note: This feature is not supported on z/VSE systems.

If you need a temporary Model 204 file, you no longer have to allocate it on disk. It can be built in memory, ATB (above the bar), using the MEMORY PAGES keywords in either the [[DEFINE DATASET command]] or [[ALLOCATE command]].

The following scenarios show how you might use in-memory files:

<ul>
<li>
You have a WORK file that applications use.
 
If this is an in-memory file, all file read (DKRD) and write (DKWR) operations merely move pages from the in-memory file to and from the buffer pool for processing just like any other file, but there is no physical disk I/O. Any updated pages will be moved (DKWR) back to the in-memory file, but that also avoids physical disk I/O.
</li>

<li>
You have a file that gets an extremely high number of updates.
 
This file can be allocated as an in-memory file and restored from a backup copy. Then it can be used by any update processes needed, and when complete, the file can be closed by all users and then dumped to the backup data set.
</li>
</ul>

All pages for an in-memory file reside in and use system memory (above the bar) while still taking advantage of the structure and capabilities of a Model 204 file.

Using an in-memory file reduces CPU time processing, such as COMMIT statements and file page loading and swapping, as the file pages remain in storage even after the last physical file close. All in-memory file pages are shared among all users via the buffer pool, like any other Model 204 file.

===Opening and closing in-memory files===
You must define the data set with the MEMORY and PAGES keywords, then
create it, open it, and initialize it. Afterward, you can use the file as you would
any other Model 204 file.
<ul>
<li>The FPL page enqueue list is maintained for in-memory files.</li>
<li>The system enqueues used to protect FPL page updates are not used for
in-memory files.</li>
</ul>
===Freeing an in-memory file===
When an in-memory file is no longer required, you can free it with the [[FREE command]].

[[Category: File management]]

In-memory files - Revision history

JAL: minor cleanup

JAL: misc formatting

Alex at 03:22, 25 February 2015

DmeWiccan: Automatically generated page update

ELowell: /* Restoring an in-memory file */

ELowell: /* Freeing an in-memory file */

JAL: minor cleanup

ELowell at 00:08, 2 July 2013

ELowell: Created page with "You can create temporary in-memory Model 204 files, which incur less CPU overhead and none of the I/O associated with permanent Model 204 files. Note: ..."

ELowell: Created page with "You can create temporary in-memory Model 204 files, which incur less CPU overhead and none of the I/O associated with permanent Model 204 files.
Note: ..."