C Converting to Oracle Real Application Clusters from Single-Instance Oracle Databases

C.1 Administrative Issues for Converting Databases to Oracle RAC

Note the following administrative considerations before converting single-instance databases to Oracle RAC:

• Backup procedures should be available before converting from a single-instance Oracle Database to Oracle RAC.

• For archiving with Oracle RAC environments, the archive file format requires a thread number.

• The archived logs from all instances of an Oracle RAC database are required for media recovery. Because of this, if you archive to a file and you do not use a cluster file system, or some other means to provide shared file systems, then you require a method of accessing the archive logs from all nodes on which the cluster database has instances.

• By default, all database files are migrated to Oracle-Managed Files (OMF). This feature simplifies tablespace creation, ensures datafile location consistency and compliance with OFA rules, and reduces human error with data file management.

C.2 Converting to Oracle RAC with DBCA

You can use Database Configuration Assistant to convert from single-instance Oracle databases to Oracle RAC. DBCA automates the configuration of the control file attributes, creates the undo tablespaces and the redo logs, and makes the initialization parameter file entries for cluster-enabled environments. It also configures Oracle Net Services, Oracle Clusterware resources, and the configuration for Oracle RAC database management for use by Oracle Enterprise Manager or the SRVCTL utility.

Before you use DBCA to convert a single-instance database to an Oracle RAC database, ensure that your system meets the following conditions:

• It is a supported hardware and operating system software configuration.

• It has shared storage: either Oracle Cluster File System or ASM is available and accessible from all nodes. On Linux on POWER systems, ensure that GPFS is available and accessible from all nodes.

• Your applications have no design characteristics that preclude their use with cluster database processing.

If your platform supports a cluster file system, then you can use it for Oracle RAC. You can also convert to Oracle RAC and use a non-shared file system. In either case, Oracle strongly recommends that you use Oracle Universal Installer (OUI) to perform an Oracle Database 11g release 1 (11.1) installation that sets up the Oracle home and inventory in an identical location on each of the selected nodes in your cluster.

This section describes the following scenarios:

• Converting Oracle Database 11g Installations to Oracle RAC Using DBCA

• Converting Single Instance on a Cluster to Oracle RAC using DBCA

• Converting Single-Instance ASM to Cluster ASM Using DBCA

select * from v$active_instances

C.3 Preparing to Convert with rconfig and Oracle Enterprise Manager

You can use rconfig, or Oracle Enterprise Manager to assist you with the task of converting a single-instance database installation to an Oracle RAC database. The first of these, rconfig, is a command line utility. Oracle Enterprise Manager Grid Control database administration option, Convert to Cluster Database, provides a GUI conversion tool. The following sections describe how to use these conversion tools:

• Prerequisites for Converting to Oracle RAC Databases

• Configuration Changes during Oracle RAC Conversion Using RCONFIG

• Converting Databases to Oracle RAC Using RCONFIG or Oracle Enterprise Manager

• Converting Databases to Oracle RAC Using Oracle Enterprise Manager

<!--ASMInfo element is required only if the current non-rac database uses ASM Storage -->
              <n:ASMInfo SID="+ASM">

> select name, state, total_mb, free_mb from v$asm_diskgroup

C.4 Converting Databases to Oracle RAC Using RCONFIG

You can use the command line utility rconfig to convert a single-instance database to Oracle RAC. To use this feature, complete the following steps:

1. As the oracle user, navigate to the directory $ORACLE_HOME/assistants/rconfig/sampleXMLs, and open the file ConvertToRAC.xml using a text editor, such as vi.

2. Review the ConvertToRAC.xml file, and modify the parameters as required for your system. The XML sample file contains comment lines that provide instructions for how to configure the file.

   Caution:

   Set the convert option Convert verify="ONLY" to perform a test conversion to ensure that a conversion can be completed successfully.

   When you have completed making changes, save the file with the syntax filename.xml. Make a note of the name you select.

3. Navigate to the directory $ORACLE_HOME/bin, and use the following syntax to run the command rconfig:

   rconfig input.xml
   

   where input.xml is the name of the XML input file you configured in step 2.

   For example, if you create an input XML file called convert.xml, then enter the following command

   $ ./rconfig convert.xml
   

If performing the conversion fails, then use the following procedure to recover and reattempt the conversion.:

1. Attempt to delete the database using the DBCA delete database option.

2. Restore the source database.

3. Review the conversion log, and fix any problems it reports that may have caused the conversion failure. The rconfig log files are under the rconfig directory in $ORACLE_BASE/cfgtoollogs.

4. Reattempt the conversion.

C.5 Example of an rconfig XML Input File for ConvertToRAC

The following is an example of an XML ConvertToRAC input file for the rconfig utility. In the example, the XML input file is for converting a single-instance database with ASM to an Oracle RAC database with ASM in the same Oracle home.

<?xml version="1.0" encoding="UTF-8"?>
<n:RConfig xmlns:n="http://www.oracle.com/rconfig"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.oracle.com/rconfig">
    <n:ConvertToRAC>   
<!-- Verify does a precheck to ensure all pre-requisites are met, before the conversion is attempted. Allowable values are: YES|NO|ONLY -->
        <n:Convert verify="YES">
<!--Specify current OracleHome of non-rac database for SourceDBHome -->
              <n:SourceDBHome>C:/oracle/rac11home</n:SourceDBHome>
<!--Specify OracleHome where the rac database should be configured. It can be same as SourceDBHome -->
              <n:TargetDBHome>C:/oracle/rac11home</n:TargetDBHome>
<!--Specify SID of non-rac database and credential. User with sysdba role is required to perform conversion -->
              <n:SourceDBInfo SID="sidb">
                <n:Credentials>
                  <n:User>sys</n:User>
                  <n:Password>oracle</n:Password>
                  <n:Role>sysdba</n:Role>
                </n:Credentials>
              </n:SourceDBInfo>
<!--ASMInfo element is required only if the current non-rac database uses ASM Storage -->
              <n:ASMInfo SID="+ASM1">
                <n:Credentials>
                  <n:User>sys</n:User> 
                  <n:Password>welcome</n:Password>
                  <n:Role>sysdba</n:Role> 
                </n:Credentials>
              </n:ASMInfo>     
<!--Specify the list of nodes that should have rac instances running. LocalNode should be the first node in this nodelist. -->
              <n:NodeList>        
                <n:Node name="node1"/>
                <n:Node name="node2"/>
              </n:NodeList>
<!--Specify prefix for rac instances. It can be same as the instance name for non-rac database or different. The instance number will be attached to this prefix. -->
              <n:InstancePrefix>sales</n:InstancePrefix>
<!--Specify port for the listener to be configured for rac database.If port="", alistener existing on localhost will be used for rac database.The listener will be extended to all nodes in the nodelist -->
              <n:Listener port="1521"/>
<!--Specify the type of storage to be used by rac database. Allowable values are CFS|ASM. The non-rac database should have same storage type. -->
              <n:SharedStorage type="CFS">
<!--Specify Database Area Location to be configured for rac database.If this field is left empty, current storage will be used for rac database. For CFS, this field will have directory path. -->
                <n:TargetDatabaseArea>M:\oradata</n:TargetDatabaseArea>
<!--Specify Flash Recovery Area to be configured for rac database. If this field is left empty, current recovery area of non-rac database will be configured for rac database. If current database is not using recovery Area, the resulting rac database will not have a recovery area. -->
                <n:TargetFlashRecoveryArea>M:\flash_sidb</n:TargetFlashRecoveryArea>
              </n:SharedStorage>
        </n:Convert>
    </n:ConvertToRAC>
</n:RConfig>

C.6 Converting Single-Instance ASM to Oracle RAC Using RCONFIG

You can use the command line utility rconfig to convert Automatic Storage Management (ASM) configured for a single-instance database to ASM configured fro Oracle RAC. To use this feature, complete the following steps:

1. As the oracle user, navigate to the directory $ORACLE_HOME/assistants/rconfig/sampleXMLs, and open the file ConvertToASM.xml using a text editor, such as vi.

2. Review the ConvertToASM.xml file, and modify the parameters as required for your system. The XML sample file contains comment lines that provide instructions for how to configure the file.

   Caution:

   Set the convert option Convert verify="ONLY" to perform a test conversion to ensure that a conversion can be completed successfully.

   When you have completed making changes, save the file with the syntax filename.xml. Make a note of the name you select.

3. Navigate to the directory $ORACLE_HOME/bin, and use the following syntax to run the command rconfig:

   rconfig input.xml
   

   where input.xml is the name of the XML input file you configured in step 2.

   For example, if you create an input XML file called convert.xml, then enter the following command

   $ ./rconfig convert.xml
   

If performing the conversion fails, then use the following procedure to recover and reattempt the conversion.:

1. Attempt to delete the ASM instance using the DBCA delete ASM option.

2. Restore the source ASM instance.

3. Review the conversion log, and fix any problems it reports that may have caused the conversion failure. The rconfig log files are under the rconfig directory in $ORACLE_BASE/cfgtoollogs.

4. Reattempt the conversion.

C.7 Example of an rconfig XML Input File for ConvertToASM

The following is an example of an XML ConvertToRAC input file for the rconfig utility. This file is available for use in the following path:

$ORACLE_HOME/assistants/rconfig/sampleXMLs 

In this example, the XML input file is for converting a single-instance database with ASM to an Oracle RAC database with ASM in the same Oracle home.

<?xml version="1.0" encoding="UTF-8"?>
<n:RConfig xmlns:n="http://www.oracle.com/rconfig"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.oracle.com/rconfig/rconfig.xsd">
                                                                           
    <n:ConvertToClusteredASM>
                <!-- Verify does a precheck to ensure all pre-requisites are met, before the conversion is attempted. Allowable values are: YES|NO|ONLY -->
        <n:ConvertASM verify="YES">
                <!--Specify current OracleHome of single instance ASM for SourceASMHome -->
              <n:SourceASMHome>/oracle/product/11.1.0/db_1</n:SourceASMHome>
                <!--Specify OracleHome where the clustered ASM should be configured. It can be same as SourceASMHome -->
              <n:TargetASMHome>/oracle/product/11.1.0/db_1</n:TargetASMHome>
                <!--Specify single instance ASM credentials -->
              <n:ASMInfo SID="+ASM">
                <n:Credentials>
                  <n:User>sys</n:User>
                  <n:Password>welcome</n:Password>
                  <n:Role>sysdba</n:Role>
                </n:Credentials>
              </n:ASMInfo>
                <!--Specify the list of nodes that should have clustered ASM instances running. LocalNode should be the first node in this nodelist. -->
              <n:NodeList>
                <n:Node name="node1"/>
                <n:Node name="node2"/>
              </n:NodeList>
                <!--Specify port for the listener to be configured for clustered ASM. If port="", listener existing on localhost will be used for clustered ASM. The listener will be extended to all nodes in the nodelist -->
              <n:Listener port=""/>
                <!--Specify comma-seperated path of ASM diskstring to discover diskgroups that will be mounted on clustered ASM instances. If this path is not accessible from a node in the nodelist, the diskgroup will not be mounted on that node. -->
              <n:ASMDiskString>/dev/raw1/*,/dev/raw2/*</n:ASMDiskString>
        </n:ConvertASM>
    </n:ConvertToClusteredASM>
</n:RConfig>

C.8 Post-Conversion Steps

After completing the conversion, note the following recommendations for Oracle RAC environments, as described in the Oracle RAC documentation:

• Follow the recommendations for using load balancing and transparent application failover, as described in Oracle Real Application Clusters Administration and Deployment Guide

• Use locally managed tablespaces instead of dictionary managed tablespaces to reduce contention and manage sequences in Oracle RAC as described in Oracle Real Application Clusters Administration and Deployment Guide

• Follow the guidelines for using automatic segment space management as described in Oracle Real Application Clusters Administration and Deployment Guide

The buffer cache and shared pool capacity requirements in Oracle RAC are slightly greater than the requirements for single-instance Oracle databases. Therefore, you should increase the size of the buffer cache by about 10%, and the size of the shared pool by about 15%.