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Large Batch Jobs

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.

Many applications require large batch jobs to make changes or to update the database system. These batch jobs usually run during the off-peak hours. Many of these jobs are run to upload data feeds into the database, and also to extract data as required for internal or external business users.

The RAC system, by providing multiple instances, allows a specific instance to be allotted to do batch jobs, without affecting the performance levels of the other instances.

Using Parallel Instance Groups

Besides the physical connection to a specific instance, there is another interesting facility that allows control over which instances allocate parallel execution server processes with instance groups. Each active instance can be assigned to at least one or more instance service groups. By activating a particular service group of instances, the instances that spawn parallel processes can be dynamically controlled.

Instance group membership can be established on an instance-by-instance basis by setting the instance_groups initialization parameter to a name representing one or more instance groups. For example, on an 8-node system owned by both marketing and HR departments, half the nodes can be assigned to one department and the other half to the other one. Either the old method of instance group assignment or the new 10g service assignments can be used.

To do this using groups, nodes 1-4 are assigned to the marketing department using the following parameter syntax in the initialization parameter file:


Nodes 5-8 are then assigned to HR using the following syntax in the parameter file:


The nodes owned by HR are activated to spawn a parallel execution server process by entering the following:


In response, Oracle allocates parallel execution server processes to nodes 5-8. The default value for parallel_instance_group is all active instances.

Services in Oracle Database 10g

Oracle Database 10g allows the user to define RAC instances as services. The services can then be individually managed and controlled. Applications are defined as a service, and the RAC instances are then assigned to the individual services. This allows the application to show affinity for a node or set of nodes.

The use of services allows for the replacement of the primary/secondary metaphor from 9i RAC with one in 10g where the primary database becomes the preferred instance while the secondary instance becomes an available instance.

The srvctl utility is used to configure the services in a RAC grid configuration. For example:

srvctl add database ?d v10g ?o $ORACLE_HOME ?s $ORACLE_HOME/dbs/v10g_spfile
srvctl add instance ?d v10g ?I v10g1 ?n aultlinux1
srvctl add instance ?d v10g ?I v10g2 ?n aultlinux2
srvctl add instance ?d v10g ?I v10g3 ?n aultlinux3
srvctl add instance ?d v10g ?I v10g4 ?n aultlinux4
srvctl add service ?d v10g ?s CRM ?r V10g1,v10g2 ?a v10g3,v10g4
srvctl add service ?d v10g ?s AR ?r v10g3,v10g4 ?a v10g1,v10g2

This would add the v10g database and its four instances, v10g1, v10g2, v10g3, and v10g4, create two services, CRM and AR, where the CRM service uses instances v10g1 and v10g2 as its preferred instances with v10g3 and v10g4 as its available instances. Service AR uses the reverse of these assignments.

The v$active_services view provides the information on what services are currently running.

Once configured, the service name can be used to define TAF and load balance configurations to allow user connections to be sent to the proper instances.


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


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