Optimize Distributed Workload - Expert Oracle RAC Performance Diagnostics and Tuning - page 487

• Functional-dependent services are based on business functions, for example, Oracle

applications, Accounts Receivable(AR), Accounts Payable(AP), General Ledger(GL), Bill of
Materials(BOM), and so forth. Here the services create a functional division of work within the
database. Such services are also termed “functional-dependent routing.”

• The third type of service that has been in use with the earlier versions of Oracle is the

PRECONNECT option in which a service spans a set of instances in the cluster. Such a service
will pre-establish a connection to more than one instance in the Oracle database to support
failover when the primary instance that the user session was originally established to fails.

Internal Services
Internal services are required and administered by Oracle for managing its resources. Internal services are primarily
two: SYS$BACKGROUND , which is used by the Oracle background processes, and SYS$USERS, which is used by user
sessions that are not associated with any service. Internal services are created by default and cannot be removed or
modified.

Server Pools
While using services gave us an opportunity to look into the application at a functional level (users performing similar
functions connect to the database as a service), in Oracle Database 11g, Oracle provides a paradigm shift by giving
us yet another option to group nodes or severs as pools of resources. A group of servers can be grouped into pools
and databases or services running in each pool can be prioritized based on the criticality of the functional areas that
access the database using that pool. What if a pool is short on resources, in this case servers, because a server crashed
or failed or the number of servers in the pool is not able to provide the resources required completing the job? Servers
from other server pools can be dynamically provisioned into the pool that needs more resources.
Figure 15-1 illustrates a server pool configuration. The configuration has three pools; each pool has three distinct
database services configured ( SSKY , OLTP , TAPS ). Pool sskypool1 and sskypool2 requires having the same number of
server definitions; however, the importance level for sskypool3 is higher compared to all other pools. This means if a
server failed in the sskypool3 and in sskypool2 , the spare server in sskypool1 is moved to sskypool3 .

Node 1 Node 2 Node 3 Node 4 Node 5 Node 6 Node 7 Node 8 Node 9 Node 10

ssky ssky ssky ssky oltp oltp taps taps

oltp taps

sskypool1
Min=3
Max=4
Importance = 10

sskypool2
Min=3
Max=3
Importance = 20

sskypool3
Min=3
Max=3
Importance = 30

Figure 15-1. Server pool configuration