5 Administering Database Instances and Cluster Databases

Overview of Administering Oracle Real Application Clusters with Enterprise Manager

Use the Web-based Enterprise Manager Database Control to manage a single Oracle RAC database. The Enterprise Manager Console provides a central point of control for the Oracle environment through a graphical user interface (GUI). You can use the Enterprise Manager Console to initiate a variety of cluster database management tasks. Use Enterprise Manager Grid Control to administer multiple Oracle RAC databases.

Enterprise Manager enables you to start, stop, and monitor databases, cluster database instances, and their Listeners, as well as to schedule jobs or set up alert thresholds for metrics. You can perform these tasks simultaneously on multiple cluster databases. You can also use the Console to manage schemas, security, and cluster database storage features.

Overview of Administering Oracle Real Application Clusters with SQL*Plus

SQL*Plus commands operate on the current instance. The current instance can be either the local default instance on which you initiated your SQL*Plus session, or it can be a remote instance to which you connect with Net Services.

Because, by default, the SQL*Plus prompt does not identify the current instance, you should direct your commands to the correct instance. Starting a SQL*Plus session and connecting to the database without specifying an instance directs all SQL*Plus commands to the local instance. In this case, the default instance is also the current instance.

To connect to a different instance in SQL*Plus, issue a new CONNECT command specify a remote instance net service name as in the following example:

CONNECT user name/password@net_service_name

SET SQLPROMPT '_CONNECT_IDENTIFIER> '

SET SQLPROMPT '_CONNECT_IDENTIFIER> '

Connecting as SYSOPER or SYSDBA enables you to perform privileged operations, such as instance startup and shutdown. Multiple SQL*Plus sessions can connect to the same instance at the same time. SQL*Plus automatically disconnects you from the first instance whenever you connect to another one.

Overview of Administering Oracle Real Application Clusters with SRVCTL

The SRVCTL tool manages configuration information that is used by several other Oracle tools. For example, Enterprise Manager uses the configuration information that SRVCTL generates to discover and monitor nodes in your cluster.

When you use SRVCTL to perform configuration operations on your cluster, SRVCTL stores configuration data in the Oracle Cluster Registry (OCR). SRVCTL performs other operations, such as starting and stopping instances, by calling SQL*Plus on each node.

Starting Up and Shutting Down with Enterprise Manager

You can shut down all instances or any identified instance from the Cluster Database Startup and Shutdown page. To start up or shut down a cluster database instance:

1. Go to the Cluster Database Home page.

2. Click the appropriate Startup or Shutdown button for your situation. If the system is down, a Startup button appears. If the system is up, a Shutdown button appears. A Specify Host and Target Database Credentials page appears.

3. Enter valid user names and passwords for host and database credentials to change the status of the database, then click OK. To change the status of the database, you must log in to the database as either SYSDBA or SYSOPER.

To start or shut down a cluster database, that is, all of the instances known to Enterprise Manager:

1. Go to the Cluster Database Home page.

2. Click Startup/Shutdown. The Specify Credentials page appears.

3. Enter a valid User Name and Password for the cluster that hosts the cluster database, then click Continue. You must be a member of the OSDBA group.

Starting Up and Shutting Down with SQL*Plus

If you want to start or stop just one instance and you are connected to your local node, you should first ensure that your current environment includes the SID for the local instance. Note that any subsequent commands in your session, whether inside or outside a SQL*Plus session, will be associated with that same SID.

To start or shutdown your local instance, initiate a SQL*Plus session and connect with the SYSDBA or SYSOPER privilege and then issue the required command. For example to start and mount an instance on your local node, run the following commands within your SQL*Plus session:

CONNECT / AS SYSDBA 
   STARTUP MOUNT

You can start more than one instance from a single SQL*Plus session on one node by way of Oracle Net Services. To achieve this, you must connect to each instance in turn by using a Net Services connection string, typically an instance-specific alias from your TNSNAMES.ORA file.

For example, you can use a SQL*Plus session on a local node to perform a transactional shutdown for two instances on remote nodes by connecting to each in turn using the instance's individual alias name. Assume the alias name for the first instance is db1 and that the alias for the second instance is db2. Connect to the first instance and shut it down as follows:

CONNECT /@db1 AS SYSDBA
   SHUTDOWN TRANSACTIONAL

Then connect to and shutdown the second instance by entering the following from you SQL*Plus session:

CONNECT /@db2 AS SYSDBA 
   SHUTDOWN TRANSACTIONAL

Other startup and shut down keywords, such as NOMOUNT, MOUNT, IMMEDIATE, and so on, are described in the SQL*Plus User's Guide and Reference

It is not possible to start up or shut down more than one instance at a time in SQL*Plus, so you cannot start or stop all of the instances for a cluster database with a single SQL*Plus command. You may wish to create a script that will connect to each instance in turn and start it up and shut it down. However, you will need to maintain this script manually if you add or drop instances.

Starting Up and Shutting Down with SRVCTL

Enter the following SRVCTL syntax from the command line, providing the required database name and instance name, or include more than one instance name to start more than one specific instance:

srvctl start instance -d db_name -i "inst_name_list" [-o start_options] [-c connect_str | -q]

Note that this command will also start all enabled and non-running services that have the listed instances either as preferred or available instances.

To stop one or more instances, enter the following SRVCTL syntax from the command line:

srvctl stop instance -d name -i "inst_name_list" [-o stop_options] [-c connect_str | -q]

This command will also stop the services related to the terminated instances on the nodes where the instances were running. As an example, the following command provides its own connection information to shut down the two instances, orcl3 and orcl4, using the IMMEDIATE option:

srvctl stop instance -d orcl -i "orcl3,orcl4" -o immediate -c "sysback/oracle as sysoper"

To start or stop your entire cluster database, that is, all of the instances and its enabled services, enter the following SRVCTL commands:

srvctl start database -d name [-o start_options] [-c connect_str | -q]

srvctl stop database -d name [-o stop_options] [-c connect_str | -q]

The following SRVCTL command, for example, mounts all of the non-running instances of an Oracle RAC database using the default connection information:

srvctl start database -d orcl -o mount

Switching Between the Automatic and Manual Policies

Use SRVCTL commands to display and change these Oracle Clusterware policies. For example, use the following command syntax to display the current policy where database_name is the name of the database for which you want to change policies:

srvctl config database -d database_name -a

Use the following SRVCTL command syntax to change the current policy to another policy where policy_name is the name of the new policy for the database that is identified by database_name:

srvctl modify database d database_name -y policy_name

This command syntax changes the resource profile values for each applicable resource and sets the Current Policy OCR key to the new value. When you add a new database using the srvctl command, you can use the -y option to specify the policy as in the following example where database_name is the name of the database and policy_name is the name of the policy:

srvctl add database -d database_name -y policy_name

This command syntax places the new database under the control of Oracle Clusterware. If you do not provide a new option, then Oracle uses the default value of automatic. After you change the policy, the OCR records the new value for the affected database.

Setting Server Parameter File Parameter Values for Oracle Real Application Clusters

You can alter SPFILE settings with Enterprise Manager or by using the SET clause of the ALTER SYSTEM statement. The examples in this section appear in ASCII text although the SPFILE is a binary file. Assume that you start an instance with an SPFILE containing the following entries:

*.OPEN_CURSORS=500
prod1.OPEN_CURSORS=1000

For the instance with the Oracle system identifier (sid) prod1, the OPEN_CURSORS parameter is set to 1000 even though it has a database-wide setting of 500. Parameter file entries that have the asterisk (*) wildcard character only affect the instances without an instance-specific entry. This gives you control over parameter settings for instance prod1. These two types of settings can appear in any order in the parameter file.

If another DBA runs the following statement, then Oracle updates the setting on all instances except the instance with sid prod1:

ALTER SYSTEM SET OPEN_CURSORS=1500 sid='*' SCOPE=MEMORY;

Then if you run the following statement on another instance, the instance with sid prod1 also assumes the new setting of 2000:

ALTER SYSTEM SET OPEN_CURSORS=2000 sid='*' SCOPE=MEMORY;

In the following example, the server parameter file contains these entries:

prod1.OPEN_CURSORS=1000
*.OPEN_CURSORS=500

Running the following statement makes Oracle disregard the first entry from the server parameter file:

ALTER SYSTEM RESET SCOPE=SPFILE;

To reset a parameter to its default value throughout your cluster database, enter the statement:

alter system reset open_cursors scope=spfile sid='prod1';

Parameter File Search Order in Oracle Real Application Clusters

Oracle searches for your parameter file in a particular order depending on your platform. On UNIX-based platforms, Oracle examines directories in the following order:

1. $ORACLE_HOME/dbs/spfilesid.ora

2. $ORACLE_HOME/dbs/spfile.ora

3. $ORACLE_HOME/dbs/initsid.ora

The search order on Windows-based platforms is:

1. %ORACLE_HOME%\database\spfilesid.ora

2. %ORACLE_HOME%\database\spfile.ora

3. %ORACLE_HOME%\database\initsid.ora

Parameters that Must Have Identical Settings on All Instances

Certain initialization parameters that are critical at database creation or that affect certain database operations must have the same value for every instance in an Oracle RAC database. Specify these parameter values in the SPFILE, or within the individual PFILEs for each instance. The following list contains the parameters must be identical on every instance:

• ACTIVE_INSTANCE_COUNT

• ARCHIVE_LAG_TARGET

• CLUSTER_DATABASE

• CLUSTER_DATABASE_INSTANCES

• CONTROL_FILES

• DB_BLOCK_SIZE

• DB_DOMAIN

• DB_FILES

• DB_NAME

• DB_RECOVERY_FILE_DEST

• DB_RECOVERY_FILE_DEST_SIZE

• DB_UNIQUE_NAME

• UNDO_MANAGEMENT

The setting for DML_LOCKS must be identical on every instance only if set to zero.

Parameters That Must Have Unique Settings on All Instances

If you use the THREAD or ROLLBACK_SEGMENTS parameters, then Oracle recommends setting unique values for them by using the sid identifier in the SPFILE. However, you must set a unique value for INSTANCE_NUMBER for each instance and you cannot use a default value.

Oracle uses the INSTANCE_NUMBER parameter to distinguish among instances at startup. Oracle uses the THREAD number to assign redo log groups to specific instances. To simplify administration, use the same number for both the THREAD and INSTANCE_NUMBER parameters.

Specify the ORACLE_SID environment variable, which comprises the database name and the number of the THREAD assigned to the instance. When you specify UNDO_TABLESPACE with automatic undo management enabled, then set this parameter to a unique undo tablespace name for each instance.

Parameters that Should Have Identical Settings on All Instances

Oracle recommends that you set the values for the following parameters to the same value on all instances. Although you can have different settings for these parameters on different instances, setting each parameter to the same value on all instances simplifies administration:

• ARCHIVE_LAG_TARGET

  Different values for instances in your Oracle RAC database are likely to increase overhead because of additional automatic synchronization performed by the database processing.

  When using Streams with your Oracle RAC database, the value should be greater than zero.

• LICENSE_MAX_USERS

  This parameter determines a database-wide limit on the number of users defined in the database and it is useful to have the same value on all instances of your database so you can see the current value no matter which instance you are using. Setting different values may cause additional warning messages to be generated during instance startup or cause commands related to database user management to fail on some instances.

• LOG_ARCHIVE_FORMAT

  If you do not use the same value for all your instances, then you unnecessarily complicate media recovery. The recovering instance expects the required archive log file names to have the format defined by its own value of LOG_ARCHIVE_FORMAT, regardless of which instance created the archive log files.

  Databases that support Data Guard, either to send or receive archive log files, must use the same value of LOG_ARCHIVE_FORMAT for all instances.

• SPFILE

  If this parameter does not identify the same file to all instances, then each instance may behave differently and unpredictably in fail over, load-balancing, as well as normal operations. Additionally, a change you make to the SPFILE with an ALTER SYSTEM SET or ALTER SYSTEM RESET command is saved only in the SPFILE used by the instance where you run the command. Your change will not be reflected in instances using different SPFILEs.

  If the SPFILE values are different in instances for which the values were set by the server, then you should restart the instances that are not using the default SPFILE.

• TRACE_ENABLED

  If you want diagnostic trace information to be always available for your Oracle RAC database, you must set TRACE_ENABLED to TRUE on all of your database instances. If you trace on only some of your instances, then diagnostic information might not be available when required should the only accessible instances be those with TRACE_ENABLED set to FALSE.

• UNDO_RETENTION

  By setting different values for UNDO_RETENTION in each instance, you are likely to reduce scalability and encounter unpredictable behavior following a fail over. Therefore, you should carefully consider whether you will accrue any benefits before you assign different values for this parameter to the instances in your Oracle RAC database.