Databases Reference
In-Depth Information
How It Works
You know that RMAN channels are nothing but database sessions that facilitate data movement. Unlike regular user
sessions, they extract data blocks and write to a target device—either disk or tape—but they are sessions nonetheless.
The trick is to spread these sessions across all the instances of the RAC cluster instead of concentrating them on only
the node where the RMAN command was given. This is where the connection to the SCAN listener comes in.
To begin, do not connect via the usual sort of command that depends upon operating system authentication:
connect target /
Instead, connect using a TNS alias as shown below:connect target rman/secretsauze@rman
Use of a TNS alias causes RMAN to connect using Oracle Net. Your session is then connected to the SCAN listener
using the service name—in this case, RMAN. You have defined the service on all the instances of the RAC cluster.
Therefore, any sessions connected to the SCAN service will be automatically spread over all the instances.
In addition, note one specific property of the service from the
srvctl config service
command given in the
solution:
Runtime Load Balancing Goal: NONE
This property ensures that the sessions will be distributed over the instances in a round-robin manner. They
will be distributed in equal numbers rather than possibly being concentrated onto nodes based on load. This even
distribution is desirable, because you won't know in advance how the nodes will be loaded over the whole period of
the RMAN backup. A relatively less loaded node might become highly loaded in the next few hours due to application
demands. If you create more RMAN sessions on that node because it is less loaded, the node might end up becoming
highly overloaded, and it might even crash or cause other performance issues.
Parallelizing a Backup Across All Nodes in a Cluster (Below 11.2)
Problem
In your pre-11.2 RAC database you have more than one node. You want to leverage the full power of all the nodes
during a backup rather than taxing only one node.
Solution
The solution is similar to that in Recipe 23-2, but unlike that recipe, this solution is for all RAC databases; it is not
restricted to Oracle 11.2 and above. Note that for databases 11.2 and above, you should choose Recipe 23-2.
1.
Put the following two TNS entries into the TNSNAMES.ORA file:
RMAN1=
(DESCRIPTION=
(LOAD_BALANCE=NO)
(ADDRESS_LIST=
(ADDRESS = (PROTOCOL =TCP)(HOST = prolin1-oravip)(PORT=1521))
(ADDRESS = (PROTOCOL =TCP)(HOST = prolin2-oravip)(PORT=1521))
)
(CONNECT_DATA =
