An entry-sequenced data set (ESDS) acts as a sequential file organization but has the advantages of being under control of VSAM, some use of direct processing, and password facilities.
The ESDS data set is in the sequence in which it is created, and you normally (but not necessarily) process from the start to the end of the data set.
How ESDS VSAM File Allows Duplicates
- The sequential processing of an ESDS by RBA is known as addressed access, which is the method you use to create the dataset.
- RBA is the method to access records in ESDS.
- ESDS is not concerned with keys. So the ESDS dataset may legally contain duplicate records.
- Assume an ESDS containing records with RBAs 001, 003, 004, and 006. The dataset would appear as follows:| 001 | 003 | 004 | 006 |
- Each record in ESDS are identified by the RBA address. So the record may be duplicate but RBA unique.
How to Use ESDS Files
ESDS for tables that are to load into programs, for small files that are always in ascending sequence, and for files extracted from a KSDS that are to be sorted.