RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Online Database Synchronization
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
7-3
Database Considerations When Synchronizing
Entire Databases
SYNCHDBTIME Issues
When you include the SYNCHDBTIME option in the INITIALIZE RDF command,
there are three special cases you might have to consider.
Enscribe Create Records
If you performed an Enscribe create operation on the backup system prior to execution
of the INITIALIZE RDF command and the extractor’s restart position in the MAT is
before the associated Enscribe create record in the MAT, the updater processing that
record will report a File System error 10 (File Already Exists) and you must purge the
existing file.
Stop-RDF-Updater Records
Stop-RDF-Updater records in the MAT are associated with committed SQL DDL
operations performed on the primary system with the SHARED ACCESS option.
Although such operations can be performed on the primary system without stopping
your applications, they must be performed manually on the backup system after all
updaters have shut down in response to the same Stop-RDF-Updater record.
As a general rule, you should not initialize the RDF/IMPX subsystem to a synchdbtime
if you recently performed a SQL operation with SHARED ACCESS on the primary
system. For example, suppose you have a SQL table (tableA) that contains the range of
keys A through Z and you just moved its partition boundary such that tableA now
contains only the keys A through M and a new table (tableB) contains the keys N
through Z. Suppose also that you performed this operation manually on the backup
system.
If you then initialize the RDF/IMPX subsystem to a point in the MAT prior to the Stop-
RDF-Updater record associated with the partition boundary change and an updater
encounters audit information associated a key N through Z, the updater will report an
error because it will try to apply the audit information to tableA (which used to contain
it, but now does not), and the audit information will not be applied to the backup
database. In this particular case the database is not corrupted, but data corruption could
occur for other SQL DDL SHARED ACCESS operations.
If you did recently perform a SQL operation with SHARED ACCESS on the primary
system and you want to initialize the RDF/IMPX subsystem to a synchdbtime, you must
specify a synchdbtime such that the starting position in the MAT is after the Stop-RDF-
Updater record.
As a precaution, if RDFCOM encounters a Stop-RDF-Updater record during its
backward search of the MAT, it issues a warning message to that effect asking if you
want to proceed with initialization. If the extractor encounters such a record while
operating in database synchronization mode, it abends..
TMF Shutdown Records
TMF shutdown records in the MAT do not cause a problem, except that RDF shuts down
and you must then restart it.