The IDMS journals are online datasets that are used by the various CV's to record before-and-after-images of database records. If a program running under the CV abends, the journal is read to restore the before-images to the database as part of its rollback recovery.
When a journal fills up, a job is automatically submitted by the CV to dump the journal to tape and erase all 'COMMITTED' images from the online journal file. Once a day a program is run for each CV to read all the archived journal files and write a new tape dataset containing all that day's journal images. Each dataset is a generation dataset whose name is of the form:
The datasets are created by the production systems just after the evening backups, at approximately 9 p.m. The datasets are created by the test systems just after the early morning backups, at approximately 3 a.m.. The blocksize of each tape is 27996.