The instance directory stores all information that pertains to a database instance. The location of the instance directory cannot be changed once it is created.
On Linux and UNIX operating systems, the instance directory is located in the INSTHOME/sqllib directory, where INSTHOME is the home directory of the instance owner. The default instance can be called anything you want within the naming rules guidelines.
On Windows operating systems, the instance directory is located under the /sqllib directory where the DB2 database product was installed. The instance name is the same as the name of the service, so it should not conflict. No instance name should be the same as another service name. You must have the correct authorization to create a service.In a partitioned database environment, the instance directory is shared between all database partition servers belonging to the instance. Therefore, the instance directory must be created on a network share drive that all computers in the instance can access.
The db2nodes.cfg file is used to define the database partition servers that participate in a DB2 instance. The db2nodes.cfg file is also used to specify the IP address or host name of a high-speed interconnect, if you want to use a high-speed interconnect for database partition server communication.