Queued Sequential Access Method
QSAM arranges records sequentially in the order that they are entered
to form sequential data sets, which are the same as those data sets
that BSAM creates. The system organizes records with other records.
QSAM anticipates the need for records based on their order. To improve
performance, QSAM reads these records into storage before they are
requested. This is called queued access. You can use QSAM with the
following data types:
- sequential data sets
- basic format sequential data sets (before z/OS 1.7 these were known as sequential data sets or more accurately as non-extended-format sequential data sets)
- large format sequential data sets
- extended-format data sets
- z/OS UNIX files
Extended-format
data sets have an internal storage format that is different from data sets that are not extended
format. The internal storage format for extended-format data sets provides more usability
characteristics, and can have better performance if the data set is striped. You can choose for an
extended-format data set to be any combination of:
- striped
- encrypted
- compressed format
- or none of those.