Rational Developer for System z
Enterprise COBOL for z/OS, Version 4.1, Programming Guide


Choosing file organization and access mode

There are several guidelines you can use to determine which file organization and access mode to use in an application.

Consider the following guidelines when choosing file organization:

Consider the following guidelines when choosing access mode:

Table 1. Summary of file organizations, access modes, and record formats of COBOL files
File organization Sequential access Random access Dynamic access Fixed length Variable length
QSAM (physical sequential) X     X X
Line sequential X     X1 X
VSAM sequential (ESDS) X     X X
VSAM indexed (KSDS) X X X X X
VSAM relative (RRDS) X X X X X
  1. The data itself is in variable format but can be read into and written from COBOL fixed-length records.

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