HP NonStop G-Series - Manual (Page 49)

SDR Operations
HP NonStop SQL DDL Replicator User’s Guide —545799-005
4-9
Replication Operations
backup, so there is no increased exposure to lost transactions on the backup in case of
a takeover.
In RDFCOM, a STATUS RDF command will show an “Update NSA Stopped” state.
Prior to SDR, this is the point where system operators would manually execute the
DDL operation and restart the RDF updaters.
If SDR is installed, it is critical to notify the operators that they should not be issuing an
RDFCOM START UPDATE command when RDF is in this state.
SDR automatically restarts the RDF updaters after it has replicated the DDL. If this
doesn’t happen promptly, you should investigate the problem with SDRCOM. If you
need to bypass the DDL operation to restart the RDF updaters, use the SDRCOM
CANCEL command.
You may also issue an RDFCOM START UPDATE command and SDR will simply not
replicate the DDL. SDR has no memory of which DDL operations have not been
replicated. It simply monitors RDF and performs the associated DDL operation when
RDF enters the “Update NSA Stopped” state.
When RDF enters the Update NSA Stopped state, the SDR updater accesses the RDF
backup copy of the depot file where the associated original DDL statement was stored.
Note that the SRU file name will have a subvolume beginning with ZASDR.
If the SRU file subvolume does not begin with ZASDR, then the audit was not
produced by SDR and SDR will ignore it. It may have been caused by a WITH
SHARED ACCESS operation occurring when SDR DDL capture is disabled. You must
deal with this situation using standard RDF (i.e., manual) methods.
Translating DDL
When the DDL has been fetched from the depot file, it is translated for execution on
the backup system. SDR uses the RDF configuration to replace file names and catalog
names with their RDF backup equivalents. SDR uses the RDF volume table, any
includes and excludes, and the mapfile if configured.
During the translation process, SDR distinguishes between the target SQL object and
any secondary file reference. The target object is the first file name in the DDL
statement, specifying the table or index or view being created or updated. All other
names, such as catalogs, partitions, physical volumes, a CREATE LIKE table, or a
table being indexed are secondary references.
If the DDL target volume is not replicated, or the target file name or subvolume is
excluded, SDR skips the operation and restarts the RDF updaters. If RDF replicates