Cascaded Redo Transport Destinations: An Example of cascade Redo transfer, cascadedredo

Cascaded Redo Transport Destinations: An Example of cascade Redo transfer, cascadedredo

The following describes some other restrictions in earlier versions based on oracle 11.2.0.2.

Cascaded redo transport transfers redo data only from other standby databases.

For example, there is one master database A and two slave databases: B and C.

Then the log is transferred to A ---> B-> C. This is Cascaded Redo Transport.

A cascaded standby database can send redo logs to one or more other standby databases (physical, logical, or snapshot standby database). A maximum of 30 standby databases can be specified.

Serial redo data transmission can reduce the pressure of primary on log transmission.

After the redo data of the master database is transmitted to cascading standby, the redo data is not transmitted to other standby immediately, but is uploaded to other standby databases only after the cascading standby application. Therefore, the redo of cascaded destination has a latency than cascading standby.

Cascading has the following two restrictions:

(1) cascading standby can only be performed on physical standby databases.

(2) Data Guard broker does not support cascaded destinations.

Configure Cascaded Destination

(1) Select a physical standby database as the cascading standby database.

(2) set the FAL_SERVER parameter in cascading standby database to primary database or other standby databases that directly receive redo data from primary database.

(3) set the LOG_ARCHIVE_DEST_n parameter in cascading standby database to specify cascaded destination and other valid parameters.

(4) set the FAL_SERVER parameter in the cascaded destination database to the cascading standby database or other standby databases that directly receive redo from the primary database.

-- Some initialization parameters when Cascaded Redo Transport is used:

-- Primary Database:

DB_UNIQUE_NAME = boston

FAL_SERVER = boston2

LOG_ARCHIVE_CONFIG = 'dg _ CONFIG = (boston, boston2, denver )'

LOG_ARCHIVE_DEST_1 = 'location = USE_DB_RECOVERY_FILE_DEST

VALID_FOR = (ALL_LOGFILES, ALL_ROLES) DB_UNIQUE_NAME = boston'

LOG_ARCHIVE_DEST_2 = 'service = boston2 SYNC

VALID_FOR = (ONLINE_LOGFILES, PRIMARY_ROLE) DB_UNIQUE_NAME = boston2'

-- Cascading Physical Standby Database:

DB_UNIQUE_NAME = boston2

FAL_SERVER = boston

LOG_ARCHIVE_CONFIG = 'dg _ CONFIG = (boston, boston2, denver )'

LOG_ARCHIVE_DEST_1 = 'location = USE_DB_RECOVERY_FILE_DEST

VALID_FOR = (ALL_LOGFILES, ALL_ROLES) DB_UNIQUE_NAME = boston2'

LOG_ARCHIVE_DEST_2 = 'service = denver

VALID_FOR = (STANDBY_LOGFILES, STANDBY_ROLE) DB_UNIQUE_NAME = denver'

-- Cascaded Physical Standby Database:

DB_UNIQUE_NAME = denver

FAL_SERVER = boston2

LOG_ARCHIVE_CONFIG = 'dg _ CONFIG = (boston, boston2, denver )'

LOG_ARCHIVE_DEST_1 = 'location = USE_DB_RECOVERY_FILE_DEST

VALID_FOR = (ALL_LOGFILES, ALL_ROLES) DB_UNIQUE_NAME = denver'