 |
|
Start Logical Oracle instance apply tips
Oracle Tips by Burleson Consulting
December 9, 2011
|
Oracle Data Guard - Log Management Services
Physical Standby Database
The following diagram shows various processes
of log management services on the physical standby database. In this
diagram, log writer is used to transfer redo log entries from the
primary to the standby database. Also, standby redo logs are created
and used at the standby site. A log switch on the primary database
triggers archiving on the standby database.
Figure 5.2 – Log management service on
physical standby database
Logical Standby Database
The logical Oracle instance
provides a unique
feature in which a database can coexist in recovery and query mode
simultaneously. The log apply service on a logical Oracle instance
uses the LogMiner engine of Oracle database. When the log apply
service is initiated on the standby database, the LogMiner engine
reads the archived redo logs from the standby_archive_dest
directory and converts these redo logs into SQL statements. These
statements are then applied to Oracle instance
by SQL Apply
operations. The log apply service can be started using:
ALTER DATABASE START LOGICAL Oracle instance
APPLY;
When this statement is executed in the standby
database, it starts a Logical Standby Process (LSP) which controls
the MRP on the standby site.
The following diagram shows the complete log
management service on a logical standby database. In this case, LGWR
is configured for log transport.
Figure 5.3 – Showing Log Management Services
on Logical Standby Database
|
