Record level locking and concurrency control - Revision history

Alex: /* Release Imagine Records statement */

2025-09-05T21:49:56Z

Release Imagine Records statement

← Older revision		Revision as of 21:49, 5 September 2025
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	<p>		<p>
	Unlike <var>Model 204</var> transactions, [[Imagine Transparency]] transactions include retrieval operations. An attempt to retrieve a record that has been updated after the start of the <var>Imagine</var> transaction results in a data consistency request canceling error. If this is a concern, a <var>Release Imagine Records</var> would end the current <var>Imagine</var> transaction and a new one would be started on the next <var>Imagine</var> retrieval (or update) operation. Of course, this <var>Release Imagine Records</var> statement would have other significant application impacts, so might not be a feasible solution to avoiding data consistency errors in many cases.		Unlike <var>Model 204</var> transactions, [[Imagine Transparency]] transactions include retrieval operations. An attempt to retrieve a record that has been updated after the start of the <var>Imagine</var> transaction results in a data consistency request canceling error. If this is a concern, a <var>Release Imagine Records</var> would end the current <var>Imagine</var> transaction and a new one would be started on the next <var>Imagine</var> retrieval (or update) operation. Of course, this <var>Release Imagine Records</var> statement would have other significant application impacts, so might not be a feasible solution to avoiding data consistency errors in many cases.
			</p>
			<p>
			The <var>Release Imagine Records</var> statement, like the <var>Imagine Transparency</var> feature, is available in <var>Model 204 V8.0</var> and later.
	</p>		</p>

Alex: /* Release Imagine Records statement */

2025-09-05T20:41:54Z

Release Imagine Records statement

← Older revision		Revision as of 20:41, 5 September 2025
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	<p>		<p>
	[[Imagine Transparency]] record numbers are thread-specific and are assigned sequentially, starting at 1, as records are found or accessed. One can the use [[Record loops#For Record Number processing\|For Record Number]] statement to access the same <var>Imagine</var> record over transaction boundaries, though the record would be re-retrieved from the broker for each transaction. This is no longer possible after a <var>Release Imagine Records</var> statement is executed. On the plus side, this clears the record number to record mapping table which would, otherwise, grow indefinitely on a logged in thread. So, for long-lived threads, it is a good idea to do a <var>Release Imagine Records</var> whenever possible, to keep the mapping table small.		[[Imagine Transparency]] record numbers are thread-specific and are assigned sequentially, starting at 1, as records are found or accessed. One can the use [[Record loops#For Record Number processing\|For Record Number]] statement to access the same <var>Imagine</var> record over transaction boundaries, though the record would be re-retrieved from the broker for each transaction. This is no longer possible after a <var>Release Imagine Records</var> statement is executed. On the plus side, this clears the record number to record mapping table which would, otherwise, grow indefinitely on a logged in thread. So, for long-lived threads, it is a good idea to do a <var>Release Imagine Records</var> whenever possible, to keep the mapping table small.
			</p>
			<p>
			Unlike <var>Model 204</var> transactions, [[Imagine Transparency]] transactions include retrieval operations. An attempt to retrieve a record that has been updated after the start of the <var>Imagine</var> transaction results in a data consistency request canceling error. If this is a concern, a <var>Release Imagine Records</var> would end the current <var>Imagine</var> transaction and a new one would be started on the next <var>Imagine</var> retrieval (or update) operation. Of course, this <var>Release Imagine Records</var> statement would have other significant application impacts, so might not be a feasible solution to avoiding data consistency errors in many cases.
	</p>		</p>

Alex: /* Release Imagine Records statement */

2025-09-05T20:21:34Z

Release Imagine Records statement

← Older revision		Revision as of 20:21, 5 September 2025
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	</ul>		</ul>

			<p>
			Outside of being a bit more concise than having a separate <var>Backout</var> statement, doing a <code>Release Imagine Records Backout</code> does not result in a <code>M204.1096: There were no updates for backout to process</code> message if there are no updates.
			</p>
			<p>
			[[Imagine Transparency]] record numbers are thread-specific and are assigned sequentially, starting at 1, as records are found or accessed. One can the use [[Record loops#For Record Number processing\|For Record Number]] statement to access the same <var>Imagine</var> record over transaction boundaries, though the record would be re-retrieved from the broker for each transaction. This is no longer possible after a <var>Release Imagine Records</var> statement is executed. On the plus side, this clears the record number to record mapping table which would, otherwise, grow indefinitely on a logged in thread. So, for long-lived threads, it is a good idea to do a <var>Release Imagine Records</var> whenever possible, to keep the mapping table small.
			</p>

	====Syntax====		====Syntax====
	<p>		<p>

Alex: /* Release All Records statement */

2025-09-05T20:08:58Z

Release All Records statement

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 <p>
 The <var>Release All Records</var> statement is supported in remote file and scattered group contexts.</p>
 ===RELEASE and COMMIT RELEASE statements with global foundsets and lists===

JAL: /* Commit statement */ link repair

2018-07-23T18:54:03Z

Commit statement: link repair

← Older revision		Revision as of 18:54, 23 July 2018
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	==<b id="COMMIT statement"></b><b id="commit"></b>Commit statement==		==<b id="COMMIT statement"></b><b id="commit"></b>Commit statement==
	<p>		<p>
	A <var>Commit</var> statement ends the current transaction, dequeues checkpoints, and drops all LPU locks and exclusive record locks obtained by update statements (<var>[[Add statement\|Add]]</var>, <var>[[Change statement\|Change]]</var>, <var>[[Delete statement\|Delete]]</var>) for all files participating in the transaction.		A <var>Commit</var> statement ends the current transaction, dequeues checkpoints, and drops all LPU locks and exclusive record locks obtained by update statements (<var>[[Add statement\|Add]]</var>, <var>[[Change statement\|Change]]</var>, <var>[[Data maintenance#Delete statement\|Delete]]</var>) for all files participating in the transaction.
	The <var>Commit</var> statement does not release record locks obtained by the <var>[[Find statement (find records)\|Find]]</var> statement. The share record lock obtained by the <var>[[For Record Number statement\|For Record Number]]</var> statement is not released by a <var>Commit</var> statement executed inside a loop.</p>		The <var>Commit</var> statement does not release record locks obtained by the <var>[[Find statement (find records)\|Find]]</var> statement. The share record lock obtained by the <var>[[For Record Number statement\|For Record Number]]</var> statement is not released by a <var>Commit</var> statement executed inside a loop.</p>
	<p>		<p>

JAL: /* RELEASE RECORDS statement */ mixed case the stmt name

2018-04-24T22:28:29Z

RELEASE RECORDS statement: mixed case the stmt name

← Older revision		Revision as of 22:28, 24 April 2018
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	In the preceding example, the first FIND AND RESERVE statement prevents access to TOTAL PREMIUM while its corresponding VEHICLE PREMIUMs are being changed. </p>		In the preceding example, the first FIND AND RESERVE statement prevents access to TOTAL PREMIUM while its corresponding VEHICLE PREMIUMs are being changed. </p>

	===~~RELEASE RECORDS~~ statement===		===Release Records statement===
	<p>		<p>
	Records found using the ~~FIND AND RESERVE~~ statement are held in exclusive status until the end of the request or until they are released explicitly by the user with the ~~RELEASE RECORDS~~ statement. The ~~RELEASE RECORDS~~ statement also can be used to release records from ~~SORT~~ statements or records obtained in share status by ~~FIND~~ statements issued in the regular form. Records released in this manner are no longer available to the request and might have to be found again. The original found set or list from which the sorted set was built is not affected. </p>		Records found using the <var>Find And Reserve</var> statement are held in exclusive status until the end of the request or until they are released explicitly by the user with the <var>Release Records</var> statement. The <var>Release Records</var> statement also can be used to release records from <var>Sort</var> statements or records obtained in share status by <var>Find</var> statements issued in the regular form. Records released in this manner are no longer available to the request and might have to be found again. The original found set or list from which the sorted set was built is not affected. </p>

	<p class="note"><b>Note:</b> To avoid producing confusing results, issue a ~~RELEASE RECORDS~~ statement at the end of a loop and not in the middle of one, since the statement relinquishes control of a found set. </p>		<p class="note"><b>Note:</b> To avoid producing confusing results, issue a <var>Release Records</var> statement at the end of a loop and not in the middle of one, since the statement relinquishes control of a found set. </p>

	====Syntax====		====Syntax====
	<p>		<p>
	The format of the ~~RELEASE RECORDS~~ statement is:</p>		The format of the <var>Release Records</var> statement is:</p>
	~~<p class="~~syntax~~">RELEASE RECORDS {IN <span class="term">label</span> \| ON [LIST] <span class="term">listname</span>~~}		{{Template:Release Records statement syntax}}
	~~</p>~~
	<p>		<p>
	where label is the statement label of the FIND statement that locked the records.</p>		where <var class="term">label</var> is the statement label of the FIND statement that locked the records.</p>
	<p>		<p>
	The ~~RELEASE RECORDS~~ statement is supported in remote file and scattered group contexts.</p>		The <var>Release Records</var> statement is supported in remote file and scattered group contexts.</p>

	====Processing====		====Processing====
	<p>		<p>
	The ~~RELEASE RECORDS~~ statement removes all:</p>		The <var>Release Records</var> statement removes all:</p>
	<ul>		<ul>
	<li>Entries from the specified found set(s), thereby removing the record set lock</li>		<li>Entries from the specified found set(s), thereby removing the record set lock</li>
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	</ul>		</ul>
	<p>		<p>
	When the ~~RELEASE~~ statement refers to a ~~SORT~~ statement, the space occupied by the temporary sorted record copies is released.</p>		When the <var>Release</var> statement refers to a <var>Sort</var> statement, the space occupied by the temporary sorted record copies is released.</p>
	<p>		<p>
	~~RELEASE RECORDS ON~~ is equivalent to the ~~CLEAR LIST~~ statement. </p>		<var>Release Records On</var> is equivalent to the <var>Clear List</var> statement. </p>

	===Release All Records statement===		===Release All Records statement===

JAL: /* Syntax */ substitute a template for syntax

2018-04-24T22:05:27Z

Syntax: substitute a template for syntax

← Older revision		Revision as of 22:05, 24 April 2018
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	<p>		<p>
	The format of this release statement is:</p>		The format of this release statement is:</p>
	~~<p class="syntax">~~Release All Records		{{Template:Release All Records statement syntax}}
	~~</p>~~
	<p>		<p>
	The <var>Release All Records</var> statement is supported in remote file and scattered group contexts.</p>		The <var>Release All Records</var> statement is supported in remote file and scattered group contexts.</p>

JAL: link repair

2018-04-24T21:39:23Z

link repair

← Older revision		Revision as of 21:39, 24 April 2018
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	===Release option===		===Release option===
	<p>		<p>
	The <var>Release</var> option of the <var>Commit</var> statement performs all the operations of the <var>Commit</var> and <var>[[~~Release_all_records~~ statement\|~~Release_all_records~~]]</var> statements. :</p>		The <var>Release</var> option of the <var>Commit</var> statement performs all the operations of the <var>Commit</var> and <var>[[Release All Records statement\|Release All Records]]</var> statements:</p>
	<table>		<table>
	<tr class="head">		<tr class="head">

JAL: /* RELEASE ALL RECORDS statement */ mixed case the stmt name

2018-04-24T21:34:31Z

RELEASE ALL RECORDS statement: mixed case the stmt name

← Older revision		Revision as of 21:34, 24 April 2018
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	====FIND statement====		====FIND statement====
	<p>		<p>
	The ~~FIND~~ statement immediately locks the set of records it has retrieved in share mode. If the locking is successful, none of the records in that set can be updated by another user until the entire request, including request continuation(s), has been completed or the records have been released by some form of the ~~RELEASE~~ statement, such as ~~RELEASE RECORDS IN~~..., ~~RELEASE ALL RECORDS~~, ~~RELEASE COMMIT~~.</p>		The <var>Find</var> statement immediately locks the set of records it has retrieved in share mode. If the locking is successful, none of the records in that set can be updated by another user until the entire request, including request continuation(s), has been completed or the records have been released by some form of the <var>Release</var> statement, such as <var>Release Records In</var>..., <var>Release All Records</var>, <var>Release Commit</var>.</p>
	<p>		<p>
	A ~~FIND~~ statement executed in a loop releases the old found set as soon as the statement is re-executed. The final set selected by the ~~FIND~~ remains locked until the end of the request. An unlabeled ~~FIND~~ statement, such as a ~~FIND AND PRINT COUNT~~ statement, does not lock records at all.</p>		A <var>Find</var> statement executed in a loop releases the old found set as soon as the statement is re-executed. The final set selected by the <var>Find</var> remains locked until the end of the request. An unlabeled <var>Find</var> statement, such as a <var>Find And Print Count</var> statement, does not lock records at all.</p>

	====FIND WITHOUT LOCKS statement====		====FIND WITHOUT LOCKS statement====

JAL: /* RELEASE ALL RECORDS statement */ mixed case the stmt name

2018-04-24T21:30:11Z

RELEASE ALL RECORDS statement: mixed case the stmt name

← Older revision		Revision as of 21:30, 24 April 2018
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	RELEASE RECORDS ON is equivalent to the CLEAR LIST statement. </p>		RELEASE RECORDS ON is equivalent to the CLEAR LIST statement. </p>

	===~~RELEASE ALL RECORDS~~ statement===		===Release All Records statement===

	====Description====		====Description====
	<p>		<p>
	A ~~RELEASE ALL RECORDS~~ statement terminates the lock in share mode placed on records by the ~~FIND~~ statement. ~~RELEASE ALL RECORDS statement~~ also clears all lists and the results of all ~~SORT~~ statements, and sets the current record number to -1. </p>		A <var>Release All Records</var> statement terminates the lock in share mode placed on records by the <var>Find</var> statement. <var>Release All Records</var> also clears all lists and the results of all <var>Sort</var> statements, and sets the current record number to -1. </p>
	<p>		<p>
	After a ~~RELEASE ALL RECORDS~~ statement is processed in a ~~FOR EACH RECORD~~ loop, subsequent references to the current record in the loop cannot find a current record. If processing returns to the top of the loop, no new record is available, and the first statement after the end of the loop is executed. </p>		After a <var>Release All Records</var> statement is processed in a <var>For Each Record</var> loop, subsequent references to the current record in the loop cannot find a current record. If processing returns to the top of the loop, no new record is available, and the first statement after the end of the loop is executed. </p>

	====Syntax====		====Syntax====
	<p>		<p>
	The format of this release statement is:</p>		The format of this release statement is:</p>
	<p class="syntax">~~RELEASE ALL RECORDS~~		<p class="syntax">Release All Records
	</p>		</p>
	<p>		<p>
	The ~~RELEASE ALL RECORDS~~ statement is supported in remote file and scattered group contexts.</p>		The <var>Release All Records</var> statement is supported in remote file and scattered group contexts.</p>

	===RELEASE and COMMIT RELEASE statements with global foundsets and lists===		===RELEASE and COMMIT RELEASE statements with global foundsets and lists===
	<p>		<p>