Editing Virtual Storage Access Method (section)

===Sequential organization===
{{further|entry-sequenced data set}}

An ESDS may have an index defined to it to enable access via keys, by defining an Alternate Index. Records in ESDS are stored in order in which they are written by address access.<ref>{{cite web
   |url=https://walton.uark.edu/enterprise/IBM/systemZ/downloads/module3/VSAM-Introductory.ppt
   |title=VSAM: introductory}}</ref><ref>{{cite web |title=Server Functionality |url=https://supportline.microfocus.com/documentation/books/tps62/mafunc.htm |quote=Sequential (VSAM ESDS – Entry Sequenced Dataset)}}</ref><ref>{{cite web
      |url=http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.469.8853&rep=rep1&type=pdf
      |quote=An ESDS VSAM data set contains records in the order in which they were entered
      |title=ABCs of z/OS System Programming Volume 3|citeseerx=10.1.1.469.8853
 }}</ref> Records are loaded irrespective of their contents and their byte addresses cannot be changed.