Dynamic service registration

Dynamic service registration allows a database instance to

identify its available services to the listener. Available service

names are determined by the following parameters:

• DB_UNIQUE_NAME, DB_NAME, and DB_DOMAIN

• SERVICE_NAMES

• INSTANCE_NAME

• LOCAL_LISTENER and REMOTE_LISTENER

Dynamic service registration is configured in the database initialization file. It does not require any configuration in the listener.ora file. If not specified, the value for the SERVICE_NAMES parameter defaults to the global database name, a name comprised of the DB_UNIQUE_NAME and DB_DOMAIN parameters in the initialization parameter file. If not explicitly defined, the DB_UNIQUE_NAME parameter defaults to the value DB_NAME. The value for the INSTANCE_NAME parameter defaults to the Oracle system identifier (SID). All of these

names can be explicitly defined to non-default values.

 

The SERVICE_NAMES parameter specifies one or more names by which clients can connect to the instance. The instance registers its service names with the listener. You can specify multiple service names to distinguish among different uses of the same database. For example:

SERVICE_NAMES=PROD,DG_PRMY,DG_RW,MAIN_REPORTING

By default, the listener registration (LREG) process registers service information with its locallistener on the default local address of TCP/IP port 1521. To have the LREG process register with a local listener that does not use TCP/IP port 1521, configure the LOCAL_LISTENER parameter in the initialization parameter file to locate the local listener

 

A remote listener is a listener residing on one computer that redirects connections to a database instance on another computer. You can configure registration to remote listeners using the REMOTE_LISTENER parameter.

 

Dynamic service registration allows the LREG process of a database instance to identify its

available services to the listener without entries in the listener.ora configuration file. The listener then acts as a port mapper for those services.

 

However, when the database instance is stopped, the listener discards all information for the dynamic services related to that database. Any attempt to establish a network session to the unknown service will usually receive the error message “ORA-12514: Listener does not currently know of service requested in connect descriptor.” Static registration allows the listener to know of a service, even if the database instance is not running. This is often important with tools and utilities that try to remotely start and stop a database instance.

 

To enable DGMGRL to restart instances during the course of broker operations, a static service must be registered with the local listener and assume a static service name of db_unique_name_DGMGRL.db_domain.

Note: Static "_DGMGRL" entries are no longer needed as of Oracle Database 12.1.0.2 in Oracle Data Guard broker configurations that are managed by Oracle Restart, RAC On Node or RAC as the broker will use the clusterware to restart an instance.

 

Example: listener.ora on Standby Hosts

Static listener entries are needed for Recovery Manager

operations:

[wnode03]$ cat $ORACLE_HOME/network/admin/listener.ora

SID_LIST_LISTENER_CLONE =

(SID_LIST =

(SID_DESC =

(ORACLE_HOME = /u01/app/oracle/product/12.1.0/dbhome_1)

(SID_NAME = MYDB1)))

LISTENER_CLONE =

(DESCRIPTION_LIST =

(DESCRIPTION =

(ADDRESS = (PROTOCOL = TCP)

(HOST = MYHOST) (PORT = 1531)(IP = FIRST))))

You can configure a new listener (if necessary) or optionally update the default listener with a static service entry for your physical standby database. This entry is needed because the instance is shut down and restarted during standby database creation using RMAN.

 

 Source : Student Guide