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View Full Version : Dbvisit propagation/replication process details


Mike Donovan
10-14-2009, 10:16 AM
The following are a set of specific questions that have been asked in relation to the propagation/replication process carried out by Dbvisit.

Question:
Some of our tables don't have Unique Key or Primary Key constraints, and some of our tables have LONG columns. Are there any data types that are not supported in replication?
Answer:
All data types are supported. There are no restrictions.

Question:
Are there any limits on the size of data including LONG and CLOB columns?
Answer:
There are no limits on the size of data including LONG and CLOB columns.

Question:
What is the impact of bulk loads ( sql-loader ) on Primary Db and its effects on replication?
Answer:
All bulk loads must use "logging" so that the information appears in the redo log files in order for the transfer to work. There is a database setting that can force all commands to become logging even if the individual statements suppress logging (see command below). The impact on the replication is difficult to quantify, but Dbvisit will queue up all updates and ensure they will all get applied on the standby database. This is a very robust process.

Question:
If the primary database has scheduler jobs then does the replicated database need to have replicated jobs as well?
Answer:
The jobs will be replicated but they will not be active on the standby database.

Question:
If the primary database has triggers then do they also need to be in target db as well?
Answer:
The standby database is an exact copy of the production database, and therefore the triggers will be there as well but they will not
be active as the standby database is not open during normal replication processing.

Question:
Are there any DDL and DML operations that are not supported - including any DDL operations on data dictionary like SYS and SYSTEM schemas?
Answer:
All DML are supported, but some DDL is not supported. To see a full list of what is propagated, and what is not, please see:
http://www.dbvisit.com/docs/Dbvisit_UserGuide5.2.htm#_Toc240541183
Please note that Dbvisit will add new datafiles and tablespaces to the standby database.

Question:
Are there any operations that don't appear in the redo logs - like nologging syntax?
Answer:
We recommend setting SQL> ALTER DATABASE FORCE LOGGING;
This ensures that all database write operations are logged and the standby database will be consistent.