Consider data integrity when using join logical files.
Unless you have a lock on the physical files used by the join logical file,
the following situations can occur:
- Your program reads a record for which there are two or more records in
a secondary file. The system supplies one record to your program.
- Another program updates the record in the primary file that your program
has just read, changing the join field.
- Your program issues another read request. The system supplies the next
record based on the current (new) value of the join field in the primary file.
These same considerations apply to secondary files as well.