NonStop SQL DDL Replicator User's Guide (Update 6)

SDR Operations
HP NonStop SQL DDL Replicator User’s Guide—545799-006
4-9
Replication Operations
Restarting RDF Update
Creating the SDR Depot Files on the Backup
The SDR depot files $vol.ZASDRnnn.SDRDEPOT contain the DDL statements
captured on the primary system. The creation of the depot files is not replicated to the
backup by RDF. When RDF first attempts to insert updates into the depot file before it
exists on the backup, it issues event 736. The SDR updater detects the event signaling
that RDF is looking for the file and creates the depot file.
Processing Stop RDF Update Audit Records
When the RDF Extractor processes an SRU audit record, it filters it based on the
associated file name. If the volume or subvolume is not protected by the RDF
configuration, the SRU record is discarded.
If the SRU record is accepted, it is sent to the RDF receiver who places it in every
updater image trail. If the SRU record is processed, it causes all RDF updaters to go
into a STOP UPDATE state, with the backup database consistent up to the point of the
associated DDL statement.
When all updaters are in STOP UPDATE state, RDF issues an EMS 908 event. When
the SRU is associated with SDR, the filename will have the form
$vol.ZASDRnnn.AAmmmmmm where nnn is the primary Expand node number, and
mmmmmm is a unique sequence number assigned by SDR.
Note that the 908 shutdowns (or suspends) do not stop normal RDF extractor-to-
receiver processing. All audit produced on the primary database is still being
transmitted and stored on the 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
Note. In versions of RDF prior to T0346H11, the RDF updaters shutdown when encountering
an SRU audit record. Starting with RDF H11, the user can set the RDF global
UPDATERNSASUSPEND to ON, causing the RDF updaters to suspend, rather than shutdown,
greatly improving the performance of SDR's replication of SQL DDL operations.