HP Integrity NonStop H-Series - Manual (Page 46)

SDR Operations
HP NonStop SQL DDL Replicator User’s Guide —545799-006
4-6
Special cases
Because there are additional files involved, there are potential issues in replicating
CREATE COLLATION relating to the use of these files.
The collation compiler input file

Since edit files are not replicated by RDF, you must ensure that the same character
processing rules are present on both systems before executing the CREATE
COLLATION on the primary system.
If the input edit file does not exist on the backup system, SDR will continue to retry
the CREATE COLLATION until the input file is created or until you cancel the
operation.

Not only must the input edit file exist on the backup system, but it must also be in
sync with the input file on the primary. Problems will occur if the primary input file is
updated and an out-of-date file still exists on the backup.
The audited collation output file
The audited updates that the collation compiler makes to its output file cause RDF to
stall, because the corresponding audited compiler output file does not exist on the
backup system.
Without SDR, the operator has to create a collation manually to allow RDF to continue
processing.
With SDR, the operator no longer needs to intervene. SDR detects the absence of the
audited file and inserts a CREATE COLLATION into the depot file, before the collation
compiler has a chance to generate its audited updates. Thus, CREATE COLLATION is
replicated before RDF encounters the compiler generated audited updates.
User Transactions
Normally, SQL creates and commits a transaction for each DDL operation. No user
transaction management is required. But, you can execute DDL in a transaction that
you create and commit. This leaves SDR with a dilemma, as it does not know the final
status of the user transaction when it is time to replicate the DDL.
Note. If you have automated the replication of non database files between your primary and
backup systems, be sure to include the collation compiler input edit file into your automatically
replicated file sets.
Caution. The downside of this strategy is that the CREATE COLLATION operation could fail
on the primary system, for example due to syntax error in the compiler input, but succeed on
the backup system. This can be avoided by making sure that both systems have the same
input edit file.