How often something needs backing up depends upon how often it changes. Broadly speaking, IBM i objects can be grouped into four levels of volatility:
Most of the IBM-supplied program product libraries do not change once installed except for new releases or PTFs, and therefore, can be backed up once and for all. They should be resaved when PTFS are installed. Library QSYS does however, contain some data that may change fairly frequently, such as authority and user profile information. This should be saved at regular intervals using the OS/400 Save System (SAVSYS) command. Device configurations and modifications to system values may also change quite frequently. Since saving QSYS is a tedious process (especially when saved to diskette) and requires a dedicated machine, it is generally easier to save a record of the changes made to QSYS rather than QSYS itself. Such changes should be kept in a CL program or spool reader. Recovery then consists of restoring the last save of QSYS and rerunning the programs to modify it.
Live application execution objects (programs, device files, message files, etc.) do not change unless a modification is made to the system. Therefore, they only need backing up when a new version of the software is implemented.
Live application data objects (database files, data areas, data queues) probably change every day, as do the objects in development libraries. Therefore, they should be backed up regularly.
If journaling is used, then the data in the journal receivers of live applications will probably change the whole time—from moment to moment, as data is entered and processed. In high volume or data critical applications, journals should be saved throughout the day or even be transferred continuously to a backup machine or machines.
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