The APOLLO providers define the legacy services (vector, coverage, map, proxy, etc.). The provider definition parameters are stored by default in the providers.fac files (see \config\erdas-apollo\providers in the shared config folder).
This can cause issues in a cluster deployment because each APOLLO node loads its providers during startup and may not be aware of any provider change or creation initiated by another node. In other words, a new service is only accessible by requesting it to the node that made the change until the provider reload occurs on the other nodes.
For solving that and avoiding manual providers restart on the other nodes, the providers can be stored in a database. To enable this feature:
 modify providers.fac for coverage and vector @ cluster shared folder, and insert the following section "<CLUSTER DB="postgresql://DBHostname:5432/user+myUser/password+myPwd/database+myDB" />" within <CONFIGURATION> ... </CONFIGURATION>
<CONFIGURATION> ... <CLUSTER DB="postgresql://DBHostname:5432/user+myUser/password+myPwd/database+myDB" /> ... </CONFIGURATION>
 restart tomcat on each nodes
 login to data manager as load balancer or any node
 Create legacy service
 New service will be automatically replicated on all the nodes.
The following shows modification for different databases (e.g., postgreSQL, oracle, sqlserver)
<CLUSTER DB="postgresql://pghostname:5432/user+pgdb_user/password+pgdb_pwd/database+db_name" /> <CLUSTER DB="oracle://oraclehostname:1521/user+schema_user/password+schema_pwd/SID+oracle_sid" /> <CLUSTER DB="sqlserver://mssqlhostname:1433/database+db_name/user+sqldb_user/password+sqldb_pwd" />
NB: This configuration works also in a standalone environment. This might be useful if you want to create/edit providers with SQL requests on the BD only (no need to access the providers files on the server).