When BSAM, QSAM, or EXCP is used to read a data set from a card reader, your program can reposition the data set upon restart. If you provide a repositioning routine, instruct the operator to position the data set to the beginning if a restart becomes necessary. The program might be designed to operate as follows:

• The program saves the first record read from the data set and keeps a count of the number of records read before each checkpoint.
• After a restart, the repositioning routine reads a record from the data set and compares it with the first record read before abnormal termination. If the records are identical, the data set has been positioned to the beginning. The routine then repositions it by reading (without otherwise processing) the number of records read before the checkpoint.