****************************************************************

* TECH NOTE CZ703.T02                                  May 1997

*

* KEYWORDS: DB-EZReorg VIA OM SET 1206 MANDATORY

*

* DB-90S RELEASE 4.3 TAPES : C70301

*

* Changing STORE options to VIA an OM set

* ---------------------------------------

*

* If a record is changed to be stored VIA a set that is Manual in the

* old schema then applications must be modified to establish currencies

* in the correct sequence to honour the new VIA prior to performing

* the database reorganisation.

*

* Example

* -------

*

* Records A and B both own Record C via sets A-C and B-C. In the

* old schema Record C is stored via A, in the new schema Record C

* is stored via Record B. Set B-C is OM.

*

* Under the old schema applications may have been coded with the

* following DML:

* STORE A

* STORE C

* STORE B

* CONNECT C to B-C

*

* Under the new schema this DML sequence will fail at STORE C

* because the record is to be stored via Record B but there is

* no currency for the owner Record B as it has not yet been stored.

* IDMS does not allow this so applications must be modified to

* perform the STORE B prior to STORE C in the sequence above.

*

* In most cases the amended applications would be implemented

* along with the reorganised database area after the unload reload.

*

* Using DB-EZReorg however the amended applications must be

* implemented before the unload reload. This is because DB-EZReorg

* has to apply the updates to the reorganised files using the journal

* data generated during the database reorganisation and roll forward

* process. The updates are applied to the new database files using the

* NEW set options. With the DML sequence above the journal data

* created by STORE C would come before the data for STORE B and

* the STORE B would fail. To ensure the journal data processed by

* DB-EZReorg is in the correct sequence, implement the amended

* applications at the quiesce point created when copying the database

* files for the reorganisation, or earlier.