entry-sequenced data set

{{Short description|IBM data record organization type}}

{{merge|Linear data set|Key-sequenced data set|Relative record data set|target=Virtual Storage Access Method|discuss=Talk:Virtual Storage Access Method#Merge suggestion|date=March 2025}}

{{No footnotes|date=December 2017}}

An entry-sequenced data set (ESDS) is a type of data set used by IBM's VSAM computer data storage system.{{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}}{{rp|5}} Records are accessed based on their sequential order, that is, the order in which they were written to the file; which means that accessing a particular record involves searching all the records sequentially until it is located, or by using a relative physical address (Relative byte address, RBA), i.e. the number of bytes from the beginning of the file to start reading.{{rp|28}}

Keys may be used to access records in an ESDS by defining an alternate index.{{rp|15}}