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.

Note:

1. This parameter functions only in a cluster with only two instances.

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. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = 'ACTIVE_INSTANCE_COUNT';

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
active_instance_count		TRUE	FALSE	FALSE	FALSE	FALSE	number of active instances in the cluster database

Oracle initializatoin parameters