Besides protecting files by means of catalog attributes, DMS offers mechanisms which prevent mutual interference between jobs that wish to process a file at the same time.
Multiple jobs may read a file simultaneously (the protection attributes of the file are, of course, still observed).
For the access methods ISAM, UPAM, FASTPAM and DIV (see the corresponding descriptions), DMS offers the “shared-update processing” function. This function permits several jobs to read and write a file concurrently. In order to avoid mutual interference, parts of the file can be locked by a specific job.
In addition to these internal mechanisms, the user himself can protect his data against multiple access by reserving volumes or files by means of the SECURE-RESOURCE-ALLOCATION command. This is particularly useful for file generation groups, where it is important to maintain data consistency between the generations (see section "Pubset backup with Snapsets").