Loading a VSAM Data Set

After a data set is defined, you can load records into it from a source data set. Depending on the type of VSAM data set being loaded, the source data set records might or might not need to be in a particular order.

Records being loaded into an entry-sequenced data set do not have to be submitted in any particular order. Entry-sequenced data set records are sequenced by their time of arrival rather than by any field in the logical record.
Fixed-length RRDS records are placed into slots specified either by a user-supplied or a VSAM-supplied relative record number. The relative record number is not part of the logical record, so it is not necessary that the records be submitted in any particular order.
Records being loaded into a key-sequenced data set must be in ascending order by key, with no duplicate keys in the input data set.
Records being loaded into a variable-length RRDS must be in ascending order by key, with no duplicate keys in the input data set. If they are loaded in sequential mode, VSAM assigns the relative record number.

With entry-sequenced or key-sequenced data sets, or RRDSs, you can load all the records either in one job or in several jobs. If you use multiple jobs to load records into a data set, VSAM stores the records from subsequent jobs in the same manner that it stored records from preceding jobs, extending the data set as required.