Rule 1 - ddl capture, Rule 2 - ddl replication, Ddl capture – HP NonStop G-Series User Manual
Page 42: Ddl capture artifacts, Rule 1 - ddl capture 4-2, Rule 2 - ddl replication 4-2, Ddl capture 4-2, Ddl capture artifacts 4-2
SDR Operations
HP NonStop SQL DDL Replicator User’s Guide —545799-005
4-2
DDL Capture
Rule 1 - DDL Capture
The “capture” or extraction of SQL DDL on any system is, and must be, completely
independent of any RDF configuration. RDF can be configured to replicate
database audit (and now SQL DDL) that was generated in the past, so SDR does
not know whether or not you will configure and start RDF on a system at some
future time. The SQL DDL must be already captured, along with the other TMF
audit, to replicate everything.
DDL capture performed by SDR is analogous to TMF capture of database updates
in the audit trail. TMF does not make any assumptions about whether or not you
intend to replicate database updates using RDF. It simply captures the updates.
The same is true of SDR capturing DDL statements; SDR has no knowledge of the
RDF configuration, and it captures all SQL DDL operations.
Rule 2 - DDL Replication
The “replication” of SQL DDL is driven by RDF. There is no independent replication
of SQL DDL by SDR unless RDF is actively replicating database updates.
You may notice SDR capturing SQL DDL on the backup system and wonder if
SDR will replicate these operations to the primary system. Replication will NOT
occur, unless you have configured and started RDF to replicate database audit
from the backup to the primary system.
Understanding and remembering these basic rules is essential to dispel
misconceptions and confusion about how SDR actually works.
DDL Capture
SDR installation modifies SQL software to enable DDL capture, but in a way that is
invisible to your applications and database maintenance activities. Installing SDR does
not change the way you use SQL. You should see no significant operational or
performance change when performing any SQL operations on the primary system.
The following paragraphs discuss topics related to the capture and storage of DDL
statements on the primary system:
DDL Capture Artifacts
There are three artifacts used by SDR to perform DDL capture:
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