Data Replication with SQL Remote
PART 3. SQL Remote Administration
CHAPTER 12. Administering SQL Remote for Adaptive Server Enterprise
Schema changes to tables being replicated by SQL Remote must be made on a quiet system. A quiet system means the following:
No transactions being replicated There can be no transactions being replicated that modify the tables that are to be altered. All transactions that modify tables being altered must be scanned from the transaction log into the stable queue before the schema is altered. This is performed by running the Message Agent normally, or using the -i -b switches. After the Message Agent completes, you can make the schema change..
Message Agent The Message Agent must be shut down when the schema change is being made.
SQL Remote Open Server If you are using the SQL Remote Open Server, it must be shut down when the schema change is being made.
Schema changes include changes to publications, such as adding articles or modifying articles. However, creating or dropping subscriptions, and adding or removing remote users do not need to be done on a quiet system.
In the Adaptive Server Enterprise transaction log, there is no information recording table structure changes: the SQL Remote log scanning process gets the table structure from the Adaptive Server Enterprise system tables. Consequently, the Message Agent cannot scan an operation from the transaction log that happened against the old table structure.
Information stored in the stable queue before the schema change uses the old table definitions and information stored after the schema change uses the new table definitions.
Passthrough mode can be used at the same time as the schema change to make sure that schema changes at remote databases occur in the correct sequence.