B
Oracle Enterprise Manager in Real Application Clusters Reference

Appendix B describes service discovery problems for Oracle Enterprise Manager in Real Application Clusters environments. Specific topics covered in this appendix are:

Resolving Service Discovery Failures

Discovery of nodes and objects by Oracle Enterprise Manager is robust and rarely fails once a correct configuration is established. Failures typically occur because the Oracle Intelligent Agent was not starting on the node or the configuration is incorrect. If starting the Oracle Intelligent Agent does not resolve the problem, the discovery failure could be due to a more serious configuration issue.

This section covers the following topics:

Understanding Discovery

To understand proper configuration, it is important to understand how discovery works. During discovery, a services.ora file on the managed nodes is created in the $ORACLE_HOME/network/agent directory on UNIX operating systems and %ORACLE_HOME%\network\admin directory on Windows NT or Windows 2000 operating systems. This file contains information about the nodes and their services (databases, instances and listeners) discovered.

Note:

Oracle8i and Oracle9i databases can co-exist on the same node. Refer to Oracle8i documentation for information on Oracle8i Discovery.

This file is created from the Real Application Clusters configuration information in the shared raw device (or shared cluster file system file maintained by the SRVCTL Utility) and the following sources on the managed nodes:

You must accurately configure each of these components so that discovery succeeds.

Note:

The following Discovery descriptions apply only to Release 9.0.1 and later. If you are running an earlier version, please refer to the corresponding editions of Real Application Clusters documentation.

oratab on UNIX and Registry on Windows NT/Windows 2000

Discovery first determines the Real Application Clusters database name and the nodes associated with the database. How it accomplishes this depends on the operating system that the managed system is running on as described under the following headings:

UNIX and oratab

On UNIX operating systems, discovery uses information in the oratab entry for the name of the cluster. The oratab entry is found in /etc/oratab or /var/opt/oracle/oratab. It contains entries of the form:

db_name:$ORACLE_HOME:N

Where db_name is the database name and $ORACLE_HOME is the Oracle home given to your database. From this entry, the database name is acquired.

Next, discovery executes the following command:

srvctl config -p db_name

Where db_name was retrieved from oratab,

On some operating systems, such as Sun Solaris, node_list defaults to the entire cluster and this parameter does not need to be explicitly set. The configuration file must exist even if it has no entries.

The Windows Registry and listener.ora

On Windows operating systems, discovery locates the listener and instance names for a node with the listener.ora file, located in $ORACLE_HOME/network/admin on UNIX operating systems and %ORACLE_HOME%\network\admin on Windows NT or Windows 2000 on the discovered nodes.

Discovery requires the following entries:

The listener address must contain a TCP/IP address that specifies the HOST value as the host name of the discovered node. This ensures that the listener actually resides on the node.
```
(description=
  (address=(protocol=tcp)(host=rachp1-pc)(port=1521)))
```
For each listener that runs on the node, the sid_LIST_listener_name entry is searched for a description (sid_DESC) that contains the instance name (sid_NAME):
```
sid_list_listener=
  (sid_list=
    (sid_desc=
      (sid_name=db1)))
```

The listener.ora file created after installation typically contains the configuration for discovery.

See Also:

Oracle9i Real Application Clusters Administration for more information on the listener.ora file.

tnsnames.ora

The tnsnames.ora file, located in $ORACLE_HOME/network/admin on UNIX operating systems and %ORACLE_HOME%\network\admin on Windows NT or Windows 2000 on the discovered nodes, is read by the discovery process to determine names and address information for the database and instances on a node.

Discovery requires the following entries:

Each instance must have an entry in tnsnames.ora file For example:

db1.us.acme.com= 
 (description= 
  (address=(protocol=tcp)(host=db1-server)(port=1521))
  (connect_data= 
    (service_name=db.us.acme.com)
    (instance_name=db1)))

The Real Application Clusters Database should have an entry. For example:

db.us.acme.com= 
 (description= 
  (load_balance=on)
  (failover=on)
  (address_list=
   (address=(protocol=tcp)(host=db1-server)(port=1521))
   (address=(protocol=tcp)(host=db2-server)(port=1521)) 
  (connect_data=
     (service_name=db.us.acme.com)))

Discovery Results

Discovery results in the creation of:

Discovered nodes and services listed in services.ora file in the
$ORACLE_HOME/network/agent directory on UNIX operating systems and %ORACLE_HOME%\network\admin directory on Windows NT or Windows 2000.

The services.ora file should contain an ops_database entry for the Real Application Clusters database, that lists the node, database address, and name of the database. The example below shows a database named db.us.acme.com running on node db1-server. The database address comes from the db.us.acme.com net service name in the tnsnames.ora file.
```
db.us.acme.com=(ops_database, db1-server, (description=(load_
balance=on)(failover=on)(address_
list=(address=(protocol=tcp)(host=db1-server) 
(port=1521))(address=(protocol=tcp)(host=db2-server)(port=1521)))(connect_
data=(service_name=db.us.acme.com)))), db.us.acme.com)
```
The services.ora file should also contain an OPS_INSTANCE entry for the instance that runs on the node. This entry identifies the:
- Name of the node
- Address of instance obtained from tnsnames.ora file
- Real Application Clusters database name to which the instance belongs
- Listener name
The example below shows the instance DB1 runs on node DB1-server, and is listened for by LISTENER_DB1-server:
```
db1.us.acme.com=(ops_instance, db1-server, 
(description=(address=(protocol=tcp)(host=db1-server)(port=1521))(connect_
data= (service_name=db.us.acme.com)(instance_name=db1))), db.us.acme.com, 
listener_db1-server)
```
Errors logged in nmiconf.log in $ORACLE_HOME/network/log directory on UNIX operating systems and %ORACLE_HOME%\network\log directory on Windows NT or Windows 2000.

Troubleshooting Discovery

Note:

Oracle Intelligent Agent must be running, and the Global Services Daemon (GSD) must be started before Discovery will function properly. Also note that the Agent must be in the same Oracle Home in which the database resides.

If the services.ora file contains an ORACLE_DATABASE entry instead of ops_database and ops_instance entries, discovery has failed. To resolve this:

Check that the database is defined correctly:

On UNIX:
1. Verify that oratab file is configured correctly.
2. Run the following command to verify proper setup:
```
srvctl config -p db_name -n node_name
```
On Windows NT or Windows 2000:
1. Check the registry entries associated with the database.
2. Run the following command to verify proper setup:
```
SRVCTL config -p db_name -n node 
```
On Unix, Windows NT, or Windows 2000, SRVCTL displays the name of the node and the instance for the node. The following example shows a node named NODE1 running an instance named DB1 with a listener named LISTENER_NODE1.
```
node1 op1
```

Inspect the listener.ora and tnsnames.ora file entries to ensure that the required entries are present.