http://debianws.lexgopc.com/wiki143/index.php?action=history&feed=atom&title=Key-sequenced_data_setKey-sequenced data set - Revision history2026-05-04T21:58:25ZRevision history for this page on the wikiMediaWiki 1.43.1http://debianws.lexgopc.com/wiki143/index.php?title=Key-sequenced_data_set&diff=1567435&oldid=previmported>AnomieBOT: Dating maintenance tags: {{Merge}}2025-03-01T11:19:00Z<p>Dating maintenance tags: {{Merge}}</p>
<p><b>New page</b></p><div>{{Short description|IBM data record organization type}}<br />
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{{merge|Linear data set|Entry-sequenced data set|Relative record data set|target=Virtual Storage Access Method|discuss=Talk:Virtual Storage Access Method#Merge suggestion|date=March 2025}}<br />
A '''key-sequenced data set''' (KSDS) is a type of [[data set (IBM mainframe)|data set]] used by [[IBM]]'s [[VSAM]] [[computer data storage]] system.<ref name="demystified">{{cite book|url=https://www.redbooks.ibm.com/redbooks/pdfs/sg246105.pdf |series=Redbooks |title=VSAM Demystified |first1=Mary |last1=Lovelace |first2=Jose |last2=Dovidauskas |first3=Alvaro |last3=Salla |first4=Valeria |last4=Sokal |chapter=Chapter 1. VSAM basics |edition=3 |publisher=IBM |date=August 2022}}</ref>{{rp|5}} Each record in a KSDS data file is embedded with a unique key.<ref name="demystified"/>{{rp|20}} A KSDS consists of two parts, the data component and a separate [[index file]] known as the index component which allows the system to physically locate the record in the data file by its key value.<ref name="demystified"/>{{rp|13}} Together, the data and index components are called a cluster.<ref name="demystified"/>{{rp|15}}<br />
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Records can be accessed randomly or in sequence and can be variable-length.<br />
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As a [[VSAM]] data set, the KSDS data and index components consist of control intervals<ref name="demystified"/>{{rp|10}} which are further organized in control areas.<ref name="demystified"/>{{rp|12}} As records are added at random to a KSDS, control intervals fill and need to be split into two new control intervals, each new control interval receiving roughly half of the records. Similarly, as the control intervals in a control area are used up, a control area will be split into two new control areas, each new control area receiving roughly half the control intervals.<ref name="demystified"/>{{rp|17}}<br />
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While a basic KSDS only has one key (the primary key), alternate indices may be defined to permit the use of additional fields as secondary keys.<ref name="demystified"/>{{rp|15}} An alternate index is itself a KSDS.<ref name="demystified"/>{{rp|16}}<br />
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==See also==<br />
*[[Entry-sequenced data set]]<br />
*[[Linear data set]]<br />
*[[Relative record data set]]<br />
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==External links==<br />
*[https://web.archive.org/web/20051023212932/http://www.lascon.co.uk/d002303.htm Lascon.co.uk]<br />
*[https://web.archive.org/web/20070311021954/http://www.redbooks.ibm.com/redbooks/SG246105/wwhelp/wwhimpl/js/html/wwhelp.htm Redbooks.ibm.com]<br />
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==References==<br />
{{Reflist}}<br />
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{{Compu-storage-stub}}<br />
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[[Category:Computer file systems]]</div>imported>AnomieBOT