INSTANCE_MODE

INSTANCE_MODE indicates whether the instance is read-write, read-only, or read-mostly.

Property	Description
Parameter type	String
Syntax	INSTANCE_MODE = { READ-WRITE | READ-ONLY | READ-MOSTLY }
Default value	READ-WRITE
Modifiable	No
Basic	No
Oracle RAC	See the Oracle RAC restrictions in the initialization parameter description below.

A READ-WRITE instance is a regular Oracle instance.

A READ-ONLY instance is an Oracle instance that can only be opened in read-only mode.

A READ-MOSTLY instance is an Oracle instance that performs very few database writes.

These restrictions apply when setting the parameter on different Oracle Real Application Clusters (Oracle RAC) instances:

1. There must be at least one running instance with INSTANCE_MODE set to READ-WRITE at any given time. If the only instance with INSTANCE_MODE set to READ-WRITE goes down, all other instances will be brought down by Oracle automatically.

2. An instance with INSTANCE_MODE set to READ-ONLY cannot be the first instance to open a database or any pluggable database (PDB) among all instances in an Oracle RAC cluster.

3. Oracle does not support co-existence of an instance with INSTANCE_MODE set to READ-ONLY and an instance with INSTANCE_MODE set to READ-MOSTLY in the same Oracle RAC cluster.