Although you can process a direct data set sequentially using either the queued access method or the basic access method, you cannot read record keys using the queued access method. When you use the basic access method, each unit of data transmitted between virtual storage and an I/O device is regarded by the system as a record. If, in fact, it is a block, you must perform any blocking or deblocking required. For that reason, the LRECL field is not used when processing a direct data set. Only BLKSIZE must be specified when you read, add, or update records on a direct data set.

If dynamic buffering is specified for your direct data set, the system will provide a buffer for your records. If dynamic buffering is not specified, you must provide a buffer for the system to use.

The discussion of direct access storage devices shows that record keys are optional. If they are specified, they must be used for every record and must be of a fixed length.