Capture Architecture
Capture Process Rule Evaluation
The Capture process either captures or
discards the changes based on the rules that the DBA defines.
The rules of extraction are defined in either a negative or
positive rule set. There are basically three levels at which
rules and rules sets are defined:
-
A Table rule captures or
discards either row changes resulting from DML changes or DDL
changes to a specified table. As a part of the table, sub set
rules act on a specific set of rows within a table.
-
A Schema rule captures or
discards either row changes resulting from DML or DDL changes to
the objects in a particular schema.
-
Global rule captures or
discards either all row changes from DML changes or all DDL
changes in the database.
The Capture Process never captures changes
in SYS, SYSTEM or CTXSYS schemas. Since the SYS and SYSTEM
maintain the data dictionary for the whole instance and they are
also specific to that instance, the tables are never part of the
Capture process.
When nologging or unrecoverable
SQL operations are used, the resulting changes are never
captured by the Capture process. This is because the
nologging operations do not create the redo entries.
