Configuring the Active Standby Pair with Read-Only Cache Groups

The Active Data Guard with asynchronous redo transport mode supports an active standby pair replication scheme that only contains replicated read-only cache groups.

All replicated read-only cache groups must be created before you create the active standby pair. You cannot exclude a replicated read-only cache group when you are creating the active standby pair and you cannot add another replicated read-only cache group to the active standby pair after creation.

When you create and configure an active standby pair to support replicated read-only cache groups, perform the following to support asynchronous Active Data Guard:

When you create the active standby pair, we recommend that you keep both the active and standby masters within the same physical site. They can be on different hosts within the same site.
If you want a read-only subscriber for disaster recovery, you can add a read-only subscriber on the same disaster recovery site as the standby Oracle database and enable the subscriber for cache groups. The subscriber that you should create when using Active Data Guard is created with a duplicate operation with the ttRepAdmin -duplicate -activeDataGuard options.
The -activeDataGuard option, which is solely for the Active Data Guard environment, enables the subscriber to keep replicated read-only cache groups intact as it would for a standby master. Since the subscriber retains these cache groups, you must provide the Oracle cache administration user name and password on the ttRepAdmin utility command line.

Note:

Alternatively, you can use the ttRepDuplicateEx C function setting the TT_REPDUP_ADG flag in ttRepDuplicateExArg.flags.

The following example creates a read-only subscriber on the disaster recovery site duplicating from the standby master providing the -activeDataGuard option, the cache administration user name and passwords.
```
ttRepAdmin -duplicate -from master2 -host node1
 -uid cacheadmin -pwd timesten -cacheuid cacheadmin -cachepwd orapwd 
 -activeDataGuard adgsubscriber
```
Create the cache environment on the primary Oracle database. You do not need to perform any of these steps on the standby Oracle database.
On the primary Oracle database, grant the Oracle cache administration user the EXECUTE privilege for the SYS.DBMS_FLASHBACK package. This privilege is granted as part of the initCacheAdminSchema.sql and grantCacheAdminPrivileges.sql scripts.
Configure the same connection attributes that you would for a TimesTen database that caches data from an Oracle database. In addition, since we are also monitoring transactions from the standby Oracle database, configure the StandbyNetServiceName connection attribute with the net service name of the standby Oracle database instance.
On Microsoft Windows systems, the net service name of the Oracle database instance is specified in the Oracle Net Service Name field of the TimesTen Cache tab within the TimesTen ODBC Setup dialog box. The standby Oracle database instance is specified in the Standby Oracle Net Service Name field on the same page.

Configure the StandbyNetServiceName ODBC.INI attribute on the active master to configure the net service name of the physical standby Oracle database:
```
[cachedb]
DataStore=/myDb/cachedb
PermSize=256
TempSize=256
DatabaseCharacterSet=WE8DEC
OracleNetServiceName=primaryinstance
StandbyNetServiceName=standbyinstance
```