FND_NODES table is present in the APPS schema.
In a muti-tier environment if we want to check the Application services which are running on different node then we can check from fnd_nodes table.

select NODE_NAME,SUPPORT_CP,SUPPORT_FORMS,SUPPORT_WEB,SUPPORT_ADMIN from FND_NODES;

NODE_NAME       SUPPORT_CP           SUPPORT_FORMS        SUPPORT_WEB          SUPPORT_ADMIN
---------------              -------------------                  --------------------                  --------------------                   --------------------
DEV01                          N                                  N                                    N                                         N
DEV02                          Y                                  Y                                     Y                                         Y


SUPPORT_CP: Concurrent Server
SUPPORT_FORMS: Form Server
SUPPORT_WEB: Apache Server
SUPPORT_ADMIN : Admin Server

Cleaning Of FND_NODES table

In the FND_NODES table at certain times we can find there useless entry present which may be the result of the cloning from production which may be the entry other than our present host. So we to need to clean up the FND_NODES table.

Steps:

1.Stop the application services.
2.Run EXEC FND_CONC_CLONE.SETUP_CLEAN; and issue commit after successful completion.
3.Now there must not be any entry present in FND_NODES table.
    select * from fnd_nodes;
    no row selected
4. Run autoconfig on DB_node.
    cd $ORACLE_HOME/appsutil/scripts
    adautocfg.sh
    It will prompts for the apps password.
5.Run autoconfig on Apps_node.
   cd $INST_TOP/admin/scripts
   adautocfg.sh
   It will prompts for the apps password.

This will populate the FND_NODES tables with the correct entry for the application and database node.