Note also the following DMS-related aspects of a realm extension:
Files can only be extended in complete allocation units. The size of the allocation unit is set by the system administrator with reference to the disk format (e.g. 3, 4, 32 PAM pages).
Each time a file extension is successfully completed, DMS doubles the value for the secondary assignment up to a maximum value. This maximum value is determined by the Class 2 system parameter DMMAXSC (global across the system for all private disks, default for pubsets) and by the following commands:
ADD-MASTER-CATALOG-ENTRY, operand MAXIMAL-ALLOCATION,
MODIFY-MASTER-CATALOG-ENTRY, operand MAXIMAL-ALLOCATION,
MODIFY-PUBSET-SPACE-DEFAULTS, operand MAXIMAL-ALLOCATION for pubsets.
If a realm file extension nearly reaches a limit, e.g. because the storage space quota of the user ID has been exhausted, then in some cases there is no partial assignment. Thus, a secondary assignment value which is too high can prevent a realm from being extended by a given number of new database pages, although this realm would otherwise have been extended successfully with a smaller secondary assignment value.
If a realm file for which online extension is to be used has been copied, the current secondary assignment setting must be checked before activating it in the session. This is recommended either when using a backup copy or before applying ALOG files for a shadow database.
If frequent file extensions are made to a realm, the file may become fragmented into a large number of extents. You should take account of this possibility by performing the necessary checks and undertaking suitable measures. For information on these issues, see the manuals "Introductory Guide to DMS" and "SPACEOPT (BS2000)").