Conditional Supplemental Groups
ALTER TABLE nydata1.allinsured ADD
SUPPLEMENTAL LOG GROUP log_group_sales (sales_id, sum_assured);
So far, the data types and supplemental
logging requirements for data replication have been presented.
Another important requirement of the Streams environment is
Object Instantiation. The following section will provide and
introduction to this concept.
Object
Instantiation and Streams
When data replication is set up for any
object, the source object needs to be instantiated. In other
words, the DBA specifies that the source database object is
ready to allow the changes to be propagated and applied on to
the destination database object. Object Instantiation is an
essential requirement in the Streams environment.
It is important to note that when the plan
is to have a table replication to the destination site, the
table must exist at the destination database. It may be possible
that the source table already has many rows and once the Streams
process begins, it can only capture the changes subsequent to
the configuration time. What about the existing rows? That is
where the instantiation of the table, schema, or database
becomes important. The Instantiation process is the method used
for creating a copy of the source object at the destination
database and setting up appropriate System Change Number (SCN)
values for replication.
There are three basic steps in
instantiating objects with Streams:
-
Prepare the object for instantiation at the
source database.
-
Ensure that a copy of the same object with the existing data or
rows is created at the destination database. This can be
achieved using export/import, the transportable tablespace
method, or the RMAN utility.
