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Oracle® Database Oracle Clusterware and Oracle Real Application Clusters Installation Guide 10g Release 2 (10.2) for Solaris Operating System Part Number B14205-04 |
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# 9 Understanding the Oracle Real Application Clusters Installed Configuration

This chapter describes the Oracle Real Application Clusters (RAC) installed configuration. This chapter contains the following topics:

- Understanding the Configured Environment in Oracle Real Application Clusters

- Oracle Cluster Registry in Oracle Real Application Clusters

- Oratab Configuration for Oracle Real Application Clusters

- Database Components Created Using Database Configuration Assistant

- Managing Undo Tablespaces in Real Application Clusters

- Initialization Parameter Files

- Configuring Service Registration-Related Parameters in Real Application Clusters

- Configuring the Listener File (listener.ora)

- Directory Server Access (ldap.ora File)

- Net Service Names (tnsnames.ora File)

- Net Services Profile (sqlnet.ora File)

## 9.1 Understanding the Configured Environment in Oracle Real Application Clusters

Oracle Net Configuration Assistant (NETCA) and Database Configuration Assistant (DBCA) configure your environment to meet the requirements for database creation and Oracle Enterprise Manager discovery of Oracle Real Application Clusters databases.

Note: Configuration files are created on each node in your cluster database.

## 9.2 Oracle Cluster Registry in Oracle Real Application Clusters

DBCA uses Oracle Cluster Registry (OCR) for storing the configurations for the cluster databases that it creates. The OCR is a shared file in a cluster file system environment. If you do not use a cluster file system, then you must make this file a shared raw device. The Oracle Universal Installer (OUI) automatically initializes the OCR during the Oracle Clusterware installation.

## 9.3 Oratab Configuration for Oracle Real Application Clusters

Oracle creates an entry for each RAC database in the `oratab` configuration file. Oracle Enterprise Manager uses this file during service discovery to determine the name of the RAC database, and to determine if the database should be automatically started when the system is restarted. The database entry has the following syntax:

    db_unique_name:$ORACLE_HOME:N

The variables `db_unique_name` is the database name for your RAC database; `$ORACLE_HOME` is the directory path to the database; and `N` indicates that the database should not be started at restart time. The following is an example entry for a database named `db`:

    db:/private/system/db:N

Note: Where the notation `db_name` appears in the previous example and throughout this chapter, it refers to the database name you entered when prompted by DBCA, or it refers to the entry you made for the `DATABASE` keyword of the `CREATE DATABASE` statement.

## 9.4 Database Components Created Using Database Configuration Assistant

This section describes the database components that DBCA creates, which include:

- Tablespaces and Data files

- Control Files

- Redo Log Files

### 9.4.1 Tablespaces and Data files

For both single-instance and cluster database environments, an Oracle Database is divided into smaller logical areas of space known as tablespaces. Each tablespace corresponds to one or more data files stored on a disk. Table 9-1 shows the tablespace names used by a RAC database and the types of data they contain:

Table 9-1 Tablespace Names Used with Real Application Clusters Databases

Tablespace Name | Contents
--- | ---
`SYSTEM` | Consists of the data dictionary, including definitions of tables, views, and stored procedures needed by the database. Oracle Database automatically maintains information in this tablespace.
`SYSAUX` | An auxiliary system tablespace that contains the `DRSYS` (contains data for OracleText), `CWMLITE` (contains the OLAP schemas), `XDB` (for XML features), `ODM` (for Oracle Data Mining), `TOOLS` (contains Enterprise Manager tables), `INDEX`, `EXAMPLE`, and `OEM-REPO` tablespaces.
`USERS` | Consists of application data. As you create and enter data into tables, Oracle Database fills this space with your data.
`TEMP` | Contains temporary tables and indexes created during SQL statement processing. You may need to expand this tablespace if you are running a SQL statement that involves significant sorting, such as `ANALYZE COMPUTE STATISTICS` on a very large table, or the constructs `GROUP BY,` `ORDER` `BY`, or `DISTINCT`.
`UNDOTBS` n | These are the undo tablespaces for each instance that DBCA creates for automatic undo management.
`RBS` | If you do not use automatic undo management, then Oracle Database uses the `RBS` tablespace for the rollback segments.

You cannot alter these tablespace names when using the preconfigured database configuration options from Oracle Universal Installer. However, you can change the names of the tablespaces if you use the advanced database creation method.

As mentioned, each tablespace has one or more data files. The data file names created by the preconfigured database configuration options vary by storage type such as ASM, OFS, raw devices, and so on.

You can specify different symbolic link names with the Advanced database configuration option.

### 9.4.2 Control Files

The database is configured with two control files that are stored on shared storage.

### 9.4.3 Redo Log Files

Each instance is configured with at least two redo log files that are stored in the shared storage. If you use a cluster file system, then these files are shared file system files. If you do not have a cluster file system, then these files are raw devices. If you use ASM, then these files are stored on the ASM disk group.

The file names of the redo log files that are created with the preconfigured database configuration options vary by storage type. You must enter the raw device names unless you are using a cluster file system.

When using raw devices, to use the advanced database creation method, locate the redo log files in the Database Storage page and replace their default filenames with the correct raw device names or symbolic link names.

## 9.5 Managing Undo Tablespaces in Real Application Clusters

Oracle Database stores rollback or undo information in undo tablespaces. To manage undo tablespaces, Oracle recommends that you use automatic undo management. Automatic undo management is an automated undo tablespace management mode that is easier to administer than manual undo management.

See Also: Oracle Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide for more information about managing undo tablespaces

## 9.6 Initialization Parameter Files

Oracle recommends using the server parameter file (SPFILE). This file resides on the server on the shared disk; all instances in a cluster database can access this parameter file.

See Also: Chapter 8, " Configuring the Server Parameter File in Oracle Real Application Clusters Environments" for more information about the creation and use of parameter files

## 9.7 Configuring Service Registration-Related Parameters in Real Application Clusters

Two key benefits of RAC are connection load balancing and failover. RAC extends the ability of single-instance Oracle Database load balancing, where connections are distributed among local dispatchers, to the balancing of connections among all instances in a cluster database. In addition, RAC provides failover by configuring multiple listeners on multiple nodes to manage client connection requests for the same database service. Connection load balancing and failover increase availability by taking advantage of the redundant resources within a cluster database. These features, however, require cross-instance registration.

Cross-instance registration in RAC occurs when an instance's process monitor (PMON) registers with the local listener, and with all other listeners. Thus, all instances in the cluster database register with all listeners that run on nodes that run instances of the cluster database. This enables all listeners to manage connections across all instances for both load balancing and failover.

Cross-instance registration requires configuring the `LOCAL_LISTENER` and `REMOTE_LISTENER` initialization parameters. The `LOCAL_LISTENER` parameter identifies the local listener, and the `REMOTE_LISTENER` parameter identifies the global list of listeners. The `REMOTE_LISTENER` parameter is dynamic. Oracle Database changes the setting for `REMOTE_LISTENER` dynamically when you reconfigure your cluster database; for example, when you add or delete instances.

By default, DBCA configures your environment with dedicated servers. However, if you select the Shared server option when using DBCA, then Oracle configures the shared server. In this case, Oracle Database uses both dedicated and shared server processing. When shared servers are configured, the `DISPATCHERS` parameter is specified as in the following example:

    DISPATCHERS="(protocol=tcp)"

If the `DISPATCHERS` initialization parameter does not specify the `LISTENER` attribute as in the previous example, then the PMON process registers information for all dispatchers with the listeners specified by the `LOCAL_LISTENER` and `REMOTE_LISTENER` parameters.

However, when the `LISTENER` attribute is specified, the PMON process registers dispatcher information with the listeners specified by the `LISTENER` attribute. In this case, setting the `LISTENER` attribute overrides `REMOTE_LISTENER` settings for the specified dispatchers as in the following example:

    DISPATCHERS="(protocol=tcp)(listener=listeners_db_name)"

See Also: Oracle Database Net Services Administrator's Guide for further information about cross instance registration, shared and dedicated server configurations, and connection load balancing

## 9.8 Configuring the Listener File (listener.ora)

You can configure two types of listeners in the `listener.ora` file as described in the following sections:

- Local Listeners

- Multiple Listeners

- How Oracle Database Uses the Listener (listener.ora File)

### 9.8.1 Local Listeners

If you configured the dedicated server mode using the DBCA Connection Mode tab on the Initialization Parameters page, then DBCA automatically configures the `LOCAL_LISTENER` parameter when the listener uses a nondefault address port.

If you configured the dedicated server mode by setting the `REMOTE_LISTENER` initialization parameter, then you must also configure the instance-specific `LOCAL_LISTENER` initialization parameter.

For example, to configure the `LOCAL_LISTENER` parameter, add the following entry to the initialization parameter file, where `listener_``sid` is resolved to a listener address through either a `tnsnames.ora` file or through the Oracle Names Server:

    sid.local_listener=listener_sid

The following entry should be in your `tnsnames.ora` file:

    listener_sid=(address=(protocol=tcp)(host=node1-vip)(port=1522))

### 9.8.2 Multiple Listeners

If DBCA detects more than one listener on the node, it displays a list of the listeners. You can select one or all of these listeners with which to register your database.

### 9.8.3 How Oracle Database Uses the Listener (listener.ora File)

Services coordinate their sessions using listener file entries by running a process on the server that receives connection requests on behalf of a client application. Listeners are configured to respond to connection requests sent to protocol addresses for a database service or non-database service.

Protocol addresses are configured in the listener configuration file, `listener.ora`, for a database service or a non-database service. Clients configured with the same addresses can connect to a service through the listener.

During a preconfigured database configuration installation, Oracle Net Configuration Assistant creates and starts a default listener called `LISTENER_``NODENAME`. The listener is configured with default protocol listening addresses for the database and external procedures. The advanced installation process prompts you to create at least one listener with Oracle Net Configuration Assistant. The listener is configured to respond to connection requests that are directed to one protocol address you specify, as well as an address for external procedures.

Both installation modes configure service information about the RAC database and external procedures. An Oracle Database 10g Release 2 (10.2) database service automatically registers its information with the listener, such as its service name, instance names, and load information.

This feature, called service registration, does not require configuration in the `listener.ora` file. After listener creation, Oracle Net Configuration Assistant starts the listener. The following is an example `listener.ora` file with an entry for an instance named `node1`:

    listener_node1=
      (description=
        (address=(protocol=ipc)(key=extproc))
        (address=(protocol=tcp)(host=node1-vip)(port=1521)(IP=FIRST))
        (address=(protocol=tcp)(host=node1-ip)(port=1521)(IP=FIRST)))
    sid_list_listener_node1=
      (sid_list=
        (sid_desc=
          (sid_name=plsextproc)
          (oracle_home=/private/system/db)
          (program=extproc)))

#### 9.8.3.1 Listener Registration and PMON Discovery

When a listener starts after the Oracle instance starts, and the listener is listed for service registration, registration does not occur until the next time the Oracle Database process monitor (PMON) discovery routine starts. By default, PMON discovery occurs every 60 seconds.

To override the 60-second delay, use the SQL ALTER SYSTEM REGISTER statement. This statement forces the PMON process to register the service immediately.

Oracle recommends that you create a script to run this statement immediately after starting the listener. If you run this statement while the listener is up and the instance is already registered, or while the listener is down, then the statement has no effect.

See Also: Oracle Database Net Services Administrator's Guide for further information about the listener and the `listener.ora` file

## 9.9 Directory Server Access (ldap.ora File)

If you configure access to a Lightweight Directory Access Protocol (LDAP)-compliant directory server with Oracle Net Configuration Assistant during a Custom Install or Advanced database configuration, an `ldap.ora` file is created. The `ldap.ora` file contains the following types of information:

- Type of directory

- Location of the directory

- Administrative context from which this server can look up, create, and modify a net service name, and database service entries

  See Also: Oracle Database Net Services Administrator's Guide for further information about directory naming configuration and directory server access configuration

## 9.10 Net Service Names (tnsnames.ora File)

A `tnsnames.ora` file is created on each node with net service names. A connect identifier is an identifier that maps to a connect descriptor. A connect descriptor contains the following information:

- The network route to the service, including the location of the listener through a protocol address

- The `SERVICE_NAME` for an Oracle release 8.1 or later, or `sid` for pre-8.1 Oracle releases

  Note: The `SERVICE_NAME` parameter you use in the `tnsnames.ora` is singular, because you can only specify one service name.

DBCA creates net service names for connections as shown in Table 9-2:

Table 9-2 Connections for Net Service Names

Net Service Name Type | Description
--- | ---
Database connections | Clients that connect to any instance of the database use the net service name entry for the database. This entry also enables Oracle Enterprise Manager to discover a RAC database. A listener address is configured for each node that runs an instance of the database. The `LOAD_BALANCE` option causes Oracle to choose the address randomly. If the chosen address fails, then the `FAILOVER` option causes the connection request to fail over to the next address. Thus, if an instance fails, then clients can still connect using another instance. In the following example, `db.us.oracle.com` is used by the client to connect to the target database, `db.us.oracle.com`.
    db.us.acme.com=
     (description=
      (load_balance=on)
       (address=(protocol=tcp)(host=node1-vip)(port=1521)
       (address=(protocol=tcp)(host=node2-vip)(port=1521)
      (connect_data=
         (service_name=db.us.acme.com)))
Note: `FAILOVER=ON` is set by default for a list of addresses. Thus, you do not need to explicitly specify the `FAILOVER=ON` parameter. When you set `DB_UNIQUE_NAME` by entering a global database name that is longer than 8 characters, excluding `DB_DOMAIN`, then a net service entry similar to the following is created:
    mydatabase.us.acme.com=
      (description =
         (address = (protocol = tcp)(host = node1-vip)(port = 1521))
         (address = (protocol = tcp)(host = node2-vip)(port = 1521))
      (load_balance = yes)
         (connect_data =
       (server = dedicated)
       (service_name = mydatabase.us.acme.com)
       )
       )
Instance connections | Clients that connect to a particular instance of the database use the net service name entry for the instance. This entry, for example, enables Oracle Enterprise Manager to discover the instances in the cluster. These entries are also used to start and stop instances. In the following example, Oracle Enterprise Manager uses `db1.us.acme.com` to connect to an instance named `db1` on `db1-server`:
    db1.us.acme.com=
     (description=
      (address=(protocol=tcp)(host=node1-vip)(port=1521))
      (connect_data=
        (service_name=db.us.acme.com)
        (instance_name=db1)))
Remote listeners | As discussed in "Configuring Service Registration-Related Parameters in Real Application Clusters", the `REMOTE_LISTENER` parameter identifies the global list of listeners and it is dynamic. Oracle Database changes the setting for `REMOTE_LISTENER` when you reconfigure your cluster database. Whether using shared servers or dedicated servers, the list of remote listeners is supplied using the `REMOTE_LISTENER` parameter. For example:
    REMOTE_LISTENER=listeners_db_unique_name
This enables the instance to register with remote listeners on the other nodes; `listeners_``db_unique_name` is resolved through a naming method such as a `tnsnames.ora` file. In the following example, `listeners_db.us.acme.com` is resolved to a list of listeners available on the nodes on which the cluster database has instances:
    listeners_db.us.acme.com=
    (address_list=
       (address=(protocol=tcp)(host=node1-vip)(port=1521))
       (address=(protocol=tcp)(host=node2-vip)(port=1521)))
The instance uses this list to determine the addresses of the remote listeners with which to register its information.
Nondefault listeners | As discussed in "Local Listeners" and "Multiple Listeners", the `LOCAL_LISTENER` parameter is set in the `init` `sid``.ora` file if a nondefault listener is configured, for example:
    sid.local_listener=listener_sid
The variable `listener_``sid` is resolved to a listener address through a naming method, such as a `tnsnames.ora` file. In the following example, `listener_db1.us.acme.com` is resolved to the nondefault listener address:
    listener_db1.us.acme.com=
       (address=(protocol=tcp)(host=node1-vip)(port=1522))
Services Entries | When you configure high availability services using the DBCA Services page, then DBCA creates net service entries similar to the following. The three services in the following examples, db_svc1, db_svc2, and db_svc3, have TAF policies of NONE, BASIC and PRECONNECT respectively.
    db_svc1.us.acme.com=
      (description =
        (address=(protocol=tcp)(host=node1-vip)(port=1521))
        (address=(protocol=tcp)(host=node2-vip)(port=1521))
        (load_balance=yes)
        (connect_data=
            (server = dedicated)
            (service_name = db_svc1.us.acme.com)
      )
      )

    db_svc2.us.acme.com=
      (description=
        (address=(protocol=tcp)(host=node1-vip)(port=1521))
        (address=(protocol=tcp)(host=node2-vip)(port=1521))
        (load_balance=yes)
        (connect_data =
            (server = dedicated)
            (service_name=db_svc2.us.acme.com)
            (failover_mode =
            (type=select)
            (method=basic)
               (retries=180)
               (delay=5)
         )
         )
         )

    db_svc3.us.acme.com=
        (description=
          (address=(protocol=tcp)(host=node1-vip)(port=1521))
          (address=(protocol=tcp)(host=node2-vip)(port=1521))
          (load_balance=yes)
          (connect_data=
            (server=dedicated)
            (service_name=db_svc3.us.acme.com)
            (failover_mode=
            (backup=db_svc3_preconnect.us.acme.com)
            (type=select)
            (method=preconnect)
            (retries=180)
            (delay=5)
       )
       )
       )
Services Entries (continued) | When a service has a TAF policy of `PRECONNECT`, then a `service_name`_`preconnect net service` entry is also created as in the following example:
    db_svc3_preconnect.us.acme.com =
      (description =
        (address = (protocol = tcp)(host = node1-vip)(port = 1521))
        (address = (protocol = tcp)(host = node2-vip)(port = 1521))
        (load_balance = yes)
        (connect_data =
          (server = dedicated)
          (service_name = db_svc3_preconnect.us.amce.com)
          (failover_mode =
            (backup = db_svc3.us.acme.com)
            (type = select)
            (method = basic)
            (retries = 180)
            (delay = 5)
          )
        )
      )
External procedures | The following is an entry for connections to external procedures. This entry enables Oracle Database to connect to external procedures.
    extproc_connection_data.us.acme.com=
     (description=
      (address_list=
        (address=(protocol=ipc)(key=extproc0))
      (connect_data=
        (sid=plsextproc)))

Example 9-1 Example tnsnames.ora File

This example is a sample `tnsnames.ora` file that is created during a preconfigured database configuration installation.

    db.us.acme.com=
     (description=
      (load_balance=on)
       (address=(protocol=tcp)(host=node1-vip)(port=1521))
       (address=(protocol=tcp)(host=node2-vip)(port=1521))
      (connect_data=
         (service_name=db.us.acme.com)))

    db1.us.acme.com=
     (description=
      (address=(protocol=tcp)(host=node1-vip)(port=1521))
      (connect_data=
        (service_name=db.us.acme.com)
        (instance_name=db1)))

    db2.us.acme.com=
     (description=
      (address=(protocol=tcp)(host=node2-vip)(port=1521))
      (connect_data=
        (service_name=db.us.acme.com)
        (instance_name=db2)))

    listeners_db.us.acme.com=
    (address_list=
       (address=(protocol=tcp)(host=node1-vip)(port=1521))
       (address=(protocol=tcp)(host=node2-vip)(port=1521)))

    extproc_connection_data.us.acme.com=
     (description=
      (address_list=
        (address=(protocol=ipc)(key=extproc)))
      (connect_data=
        (sid=plsextproc)
        (presentation=RO)))

See Also: Oracle Database Net Services Administrator's Guide for further information about the `tnsnames.ora` file

## 9.11 Net Services Profile (sqlnet.ora File)

Oracle Universal Installer starts Oracle Net Configuration Assistant after the database is installed, and creates the Net Services profile, or `sqlnet.ora` file.

By default, the `sqlnet.ora` file is located in the following directory:

    $ORACLE_HOME/network/admin

In this directory, in addition to the default `sqlnet.ora` file generated during installation, you also can find a sample sqlnet.ora file in the directory `sample`.

During installation, Oracle Net Configuration Assistant creates the following entries in the `sqlnet.ora` file:

    NAMES.DIRECTORY_PATH=(TNSNAMES, EZCONNECT)

The parameter NAMES.DIRECTORY_PATH specifies the priority order of the naming methods to use to resolve connect identifiers to connect descriptors.

The order of naming methods is as follows: directory naming (for Custom Install or Advanced database configuration options only), `tnsnames.ora` file, Easy Connect, and host naming.

The Easy Connect naming method eliminates the need for service name lookup in the tnsnames.ora files for TCP/IP environments. With Easy Connect, clients use a connect string for a simple TCP/IP address, consisting of a host name and optional port and service name. If you use this method, then no naming or directory system is required.

See Also: Oracle Database Net Services Administrator's Guide for further information about the `sqlnet.ora` file