INIT PARAMETERS NEEDED FOR RAC

INIT PARAMETERS NEEDED FOR RAC

The following Init parameters are needed in a RAC database.

1)  active_instance_count:-

Property	Description
Parameter type	Integer
Default value	There is no default value.
Modifiable	No
Range of values	1 or >= the number of instances in the cluster. (Values other than 1 have no effect on the active or standby status of any instances.)
Basic	No
Real Application Clusters	You must set this parameter for every instance, and multiple instances must have the same value.

ACTIVE_INSTANCE_COUNT enables you to designate one instance in a two-instance cluster as the primary instance and the other instance as the secondary instance. This parameter has no functionality in a cluster with more than two instances.

When you set this parameter to 1, the first instance you start up becomes the primary instance and accepts client connections. The second instance starts up as a secondary instance and can accept client connections only if the first instance fails. In such an event, the secondary instance becomes the primary instance.

When the failed instance can once again be started up, it starts up as the secondary instance, and will not accept client connections unless the current primary instance fails.

2)      cluster_database:-

Property	Description
Parameter type	Boolean
Default value	false
Modifiable	No
Range of values	true | false
Basic	Yes
Real Application Clusters	For all instances, the value must be set to TRUE.

CLUSTER_DATABASE is a Real Application Clusters parameter that specifies whether or not Real Application Clusters is enabled.

3)      cluster_database_instances:-

Property	Description
Parameter type	Integer
Default value	1
Modifiable	No
Range of values	Any nonzero value
Basic	No
Real Application Clusters	Multiple instances must have the same value.

CLUSTER_DATABASE_INSTANCES is a Real Application Clusters parameter that specifies the number of instances that are configured as part of your cluster database. You must set this parameter for every instance. Normally you should set this parameter to the number of instances in your Real Application Clusters environment. A proper setting for this parameter can improve memory use.

Oracle uses the value of this parameter to compute the default value of the LARGE_POOL_SIZE parameter when the PARALLEL_AUTOMATIC_TUNING parameter is set to true. Note that the PARALLEL_AUTOMATIC_TUNIG parameter has been deprecated.

4)      cluster_interconnects:-

Property	Description
Parameter type	String
Syntax	CLUSTER_INTERCONNECTS = ifn [: ifn ] ...
Default value	There is no default value.
Modifiable	No
Range of values	One or more IP addresses, separated by colons
Basic	No

CLUSTER_INTERCONNECTS provides Oracle with information about additional cluster interconnects available for use in Real Application Clusters environments.

The CLUSTER_INTERCONNECTS parameter can be used to override the default interconnect with a preferred cluster traffic network. This parameter is useful in Data Warehouse systems that have reduced availability requirements and high interconnect bandwidth demands. You can also use CLUSTER_INTERCONNECTS to override the default interconnect chosen by Oracle.

For example, if you are running two instances of Oracle for two databases on the same machine, then you can load balance the interconnect traffic to different physical interconnects. This does not reduce Oracle availability.

CLUSTER_INTERCONNECTS can be used in Oracle Real Application Clusters environments to indicate cluster interconnects available for use for the database traffic. Use this parameter if you need to override the default interconnect configured for the database traffic, which is stored in the cluster registry. This procedure also may be useful with Data Warehouse systems that have reduced availability requirements and high interconnect bandwidth demands.

CLUSTER_INTERCONNECTS specifically overrides the following:

• Network classifications stored by oifcfg in the OCR.
• The default interconnect chosen by Oracle.

If you want to load-balance the interconnect, then Oracle recommends that you use link-bonding at the operating system level, even if you have two databases on the same server, so that multiple interconnects use the same address. Note that multiple private addresses provide load balancing, but do not provide failover unless bonded. If you specify multiple addresses in init.ora using CLUSTER_INTERCONNECTS, instead of bonding multiple addresses at the operating system level, then typically availability is reduced, because each network interface card failure will take down that instance.

Refer to your vendor documentation for information about bonding interfaces. Some vendor bonding architectures may require the use of this parameter.

If you have multiple database instances on Oracle Real Application Clusters nodes and want to use a specific interface for each instance, then you can set theCLUSTER_INTERCONNECTS initialization parameter to the IP address for each database instance. For example:

hr1.init.ora.cluster_interconnects="192.0.2.111"

oltp3.init.ora.cluster_interconnects="192.0.2.112"

If the Oracle RAC interconnect is configured to run on a different interface than the Oracle Clusterware interconnect, then this configuration can cause reduced availability, as failovers or instance evictions can be delayed if the Oracle RAC interconnect fails while the Oracle Clusterware NIC remains up.

5)      instance_groups:-

Property	Description
Parameter type	String
Syntax	INSTANCE_GROUPS = group_name [, group_name ] ...
Default value	There is no default value.
Modifiable	No
Range of values	One or more instance group names, separated by commas
Basic	No
Real Application Clusters	Multiple instances can have different values.

INSTANCE_GROUPS is a Real Application Clusters parameter that you can specify only in parallel mode. Used in conjunction with the PARALLEL_INSTANCE_GROUP parameter, it lets you restrict parallel query operations to a limited number of instances.

This parameter specifies one or more instance groups and assigns the current instance to those groups. If one of the specified groups is also specified in the PARALLEL_INSTANCE_GROUP parameter, then Oracle allocates query processes for a parallel operation from this instance.

6)      instance_number:-

Property	Description
Parameter type	Integer
Default value	Lowest available number; derived from instance start up order and INSTANCE_NUMBER value of other instances. If not configured for Real Application Clusters, then 0.
Modifiable	No
Range of values	1 to maximum number of instances specified when the database was created
Basic	Yes
Real Application Clusters	You must set this parameter for every instance, and all instances must have different values.

INSTANCE_NUMBER is a Real Application Clusters parameter that can be specified in parallel mode or exclusive mode. It specifies a unique number that maps the instance to one free list group for each database object created with storage parameter FREELIST GROUPS.

The INSTANCE parameter of the ALTER TABLE ... ALLOCATE EXTENT statement assigns an extent to a particular free list group. If you set INSTANCE_NUMBER to the value specified for the INSTANCE parameter, the instance uses that extent for inserts and for updates that expand rows.

The practical maximum value of this parameter is the maximum number of instances specified in the CREATE DATABASE statement. The absolute maximum is operating system-dependent.

7)      lock_name_space:-

Property	Description
Parameter type	String
Syntax	LOCK_NAME_SPACE = namespace
Default value	There is no default value.
Modifiable	No
Range of values	Up to 8 alphanumeric characters. No special characters allowed.
Basic	No

LOCK_NAME_SPACE specifies the namespace that the distributed lock manager (DLM) uses to generate lock names. Consider setting this parameter if a standby or clone database has the same database name on the same cluster as the primary database.

If the standby database resides on the same file system as the primary database, then set LOCK_NAME_SPACE in the standby parameter file to a distinct value such as the following:

LOCK_NAME_SPACE = standby

8)      parallel_instance_group:-

Property	Description
Parameter type	String
Syntax	PARALLEL_INSTANCE_GROUP = group_name
Default value	A group consisting of all instances currently active
Modifiable	ALTER SESSION, ALTER SYSTEM
Range of values	Any group name specified in the INSTANCE_GROUPS parameter of any active instance
Real Application Clusters	Multiple instances can have different values.

PARALLEL_INSTANCE_GROUP is a Real Application Clusters parameter that you can specify in parallel mode only. Used in conjunction with the INSTANCE_GROUPS parameter, it lets you restrict parallel query operations to a limited number of instances.

This parameter identifies the parallel instance group Oracle will use for spawning parallel execution processes. Parallel operations will spawn parallel execution processes only on instances that specify a matching group in their INSTANCE_GROUPS parameter.

If the value of PARALLEL_INSTANCE_GROUP does not correspond to an instance group name specified for an active instance, Oracle returns an error.

9)      parallel_server:-

Parameter type:	Boolean
Parameter class:	Static
Default value:	FALSE
Range of values:	TRUE | FALSE
Oracle Parallel Server:	Multiple instances must have the same value.

PARALLEL_SERVER is an Oracle Parallel Server parameter that specifies whether Oracle Parallel Server is enabled. 

10)  parallel_server_instances:-

Parameter type:	Integer
Parameter class:	Static
Default value:	1
Range of values:	Any non-zero value

PARALLEL_SERVER_INSTANCES is an Oracle Parallel Server parameter that specifies the number of instances currently configured. You must set this parameter for every instance. Normally you should set this parameter to the number of instances in your Oracle Parallel Server environment. A proper setting for this parameter can improve memory use.

Oracle uses the value of this parameter to compute the default value of the LARGE_POOL_SIZE parameter when the PARALLEL_AUTOMATIC_TUNING parameter is set to TRUE.  

11)  thread:-

Property	Description
Parameter type	Integer
Default value	0
Modifiable	No
Range of values	0 to the maximum number of enabled threads
Real Application Clusters	If specified, multiple instances must have different values.

THREAD is a Real Application Clusters parameter that specifies the number of the redo thread to be used by an instance.
When you create a database, Oracle creates and enables thread 1 as a public thread (one that can be used by any instance). You must create and enable subsequent threads using the ADD LOGFILE THREAD clause andENABLE THREAD clause of the ALTER DATABASE statement. The number of threads you create is limited by the MAXINSTANCES parameter specified in the CREATE DATABASE statement.
In exclusive mode, thread 1 is the default thread. However, you can specify THREAD for an instance running in exclusive mode if you want to use the redo log files in a thread other than thread 1.In parallel mode, you can specify any available redo thread number, as long as that thread number is enabled and is not in use by another instance.
A value of zero specifies that this instance can use any available, enabled public thread.