Utility routines with linked-in DBH
The UDS/SQL utility routines DDL compiler, SSL compiler, BPRIVACY, BGSIA and BGSSIA process the DBDIR and DBCOM (and if necessary required COSSD), but not the user realms of the database involved. When these utility routines with linked-in DBH (= utility sessions) are executed, both the DBDIR and the DBCOM are extended dynamically if necessary. This extension is implemented independently of online extensibility being activated for these realms. However, a prerequisite is that a secondary allocation > 0 is specified in the storage space allocation for the DBDIR and/or the DBCOM. You can thus, if required, suppress automatic extension of the DBDIR or DBCOM by specifying a secondary allocation = 0.
Activation of online extensibility of the DBDIR using a DAL command is only effective for user sessions. You can still modify this activation as before using the DAL command ACT INCR or DEACT INCR of the Independent DBH. You can only influence online extensibility of the DBCOM by means of the secondary allocation.
In utility sessions with linked-in DBH extensions are performed using the default value 64 for ADDITIONAL_NR_PAGES and the value 0 for MIN_NR_FREE_PAGES for the following reasons:
The DBH only ever requests single free pages in the free page search. No large extension steps are therefore required, and neither the DBDIR nor the DBCOM becomes particularly large.
There is no parallelism in utility routine runs; consequently no allowance must be made in the form of MIN_NR_FREE_PAGES > 0.
The DBTTs of the record types in the DBDIR and DBCOM (with the exception of the DBTT of the SSIA_RECORD) are, if necessary, also automatically extended independently of activation of online extensibility which is only required for user sessions provided the requirement for the corresponding realm extension (secondary allocation > 0) is satisfied.
The dimensioning of the record types in the DBDIR and DBCOM determined at database creation is retained. The DBTTs of these record types are generally sufficiently large when they are created. The aim here is to ensure that extension of the DBTTs of these record types is restricted to exceptional cases. Otherwise the DBDIR and DBCOM would increase disproportionately in size owing to frequent DBTT extensions.
Utility routines without DBH
The UDS/SQL utility routines BCREATE, BCHANGE, BALTER, BRENAME, BREORG, BFORMAT and BINILOAD and BREORG automatically extend the realms of the database being processed when required.
Regardless of whether online extensibility is activated for these realms, the aforementioned utility routines always cause the realm to be expanded when the available free space is no longer sufficient to execute the utility routine.
However, a requirement for this is that a secondary allocation > 0 has been specified in the storage space allocation for the realm concerned. Consequently you can, if you wish, suppress automatic realm extension by specifying a secondary allocation = 0.
The general conditions described in section “DMS-related aspects of online realm extension” also apply.
The realm concerned is extended by as many database pages as fit into the secondary allocation currently set in DVS, but at least by the default value of 64 pages (another 64 pages can be added if a new FPA extent is required).
If the request for a larger contiguous area of free space in the existing realm cannot be satisfied when the utility routine is executed, the size of this area is taken as the yardstick for the extension (here, too, the number of pages which can be fitted into the secondary allocation and the default value 64 are not fallen below).
The execution of automatic realm extension, its scope and the new size of the realm are shown by the following messages:
0074 REALM <realmname> HAS BEEN EXTENDED BY nnn DATABASE-PAGES
NEW NR OF PAGES : mmm
Failure of automatic realm extension results in the following message being issued:
0073 DYNAMIC EXTENSION BY nnn DATABASE-PAGES NOT POSSIBLE FOR REALM <realmname>