http://70.231.62.181/index.php?action=history&feed=atom&title=Queued_Sequential_Access_MethodQueued Sequential Access Method - Revision history2026-04-23T06:03:02ZRevision history for this page on the wikiMediaWiki 1.45.1http://70.231.62.181/index.php?title=Queued_Sequential_Access_Method&diff=2496027&oldid=previmported>Truthanado: c/e, grammar2023-09-16T22:44:54Z<p>c/e, grammar</p>
<p><b>New page</b></p><div>{{Short description|Access method to read and write datasets sequentially}}<br />
In [[IBM mainframe]] [[operating system]]s, '''Queued Sequential Access Method''' ('''QSAM''')<ref>{{cite manual|publisher=IBM|title=IBM System/360 Operating System Sequential Access Methods Program Logic Manual|id=Y28-6604-1|date=January 1967|url=http://www.bitsavers.org/pdf/ibm/360/os/plm_1966-67/Y28-6604-1_Sequential_Access_Methods_PLM_Jan67.pdf}}</ref> is an [[access method]] to read and write [[data set (IBM mainframe)|dataset]]s sequentially. QSAM is available on [[OS/360]], [[OS/VS2]], [[MVS]], [[z/OS]], and related operating systems.<br />
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QSAM is used both for devices that are naturally sequential, such as [[punched card]] readers and punches and line printers, and for data on devices that could also be addressed directly, such as [[magnetic disk]]s. QSAM offers device independence: to the extent possible, the same [[Application programming interface|API]] calls are used for different devices.<br />
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QSAM is—as its name says—queued, in this specific context meaning buffered with deblocking of reads and blocking of writes. It allows programs to read and write logical records within physical blocks of data, as opposed to the less advanced [[basic sequential access method]] (BSAM) which allows programs to access physical blocks of data, but provides no support for accessing logical records within blocks.<br />
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QSAM manages truncated final blocks and truncated embedded blocks completely transparently to the user.<br />
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The QSAM application program interface can be compared with the interface offered by ''open'', ''read'', ''write'' and ''close'' calls (using file handles) in other operating systems such as [[Unix]] and [[Microsoft Windows|Windows]].<br />
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==See also==<br />
*[[Sequential access memory]] (SAM)<br />
*[[Basic sequential access method]] (BSAM)<br />
*[[Hierarchical sequential access method]] (HSAM)<br />
*[[Basic indexed sequential access method]] (BISAM)<br />
*[[Queued indexed sequential access method]] (QISAM)<br />
*[[Hierarchical indexed sequential access method]] (HISAM)<br />
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==References==<br />
{{Reflist}}<br />
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{{Mainframe I/O access methods}}<br />
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[[Category:IBM mainframe operating systems]]</div>imported>Truthanado