The UDS online utility offers the option of online execution (i.e. while the DBH is operating) of some functions for compressing databases, some of which are otherwise implemented by utility routines with comparable functions.
You can compress databases offline as follows:
using BPGSIZE (see the “Creation and Restructuring” manual) or
by unloading and reloading the data using BOUTLOAD/BINILOAD (see the “Creation and Restructuring” manual) or
by creating tables with BREORG (see the chapter “Database reorganization with BREORG”).
The UDS online utility enables you to relocate and compress records and tables specifically in various realms and during ongoing operation. Furthermore, whole data pages which contain the records of a distributable list can be relocated from one realm to another during ongoing operation.
When data is compressed with BPGSIZE or BOUTLOAD/BINILOAD, locks of DBTT entries (cf. the KEEP statement of the utility routine BMODTT) are canceled; these locks are retained when compression takes place with the UDS online utility.
With the UDS online utility you can change the free place search in the realm and thus also call the comparable functions SET and RESET of the BMODTT utility routine (see "Controlling the reuse of database keys and the free place search with BMODTT") and make them effective during live operation.
For distributable lists the UDS online utility enables you to change the preferred realm during ongoing operation, i.e. the realm in which the DBH searches for pages which are currently free for storage purposes.
The UDS online utility enables you to update probable position pointers (PPP) to the most recent values during ongoing operation.