25 Creating Transportable Tablespace Sets

Purpose of Creating Transportable Tablespace Sets

A transportable tablespace set contains datafiles for a set of tablespaces and an export file containing structural metadata for the set of tablespaces. The export file is generated by Data Pump Export.

One use of transportable tablespace sets is to create a tablespace repository. For example, if you have a database with some tablespaces used for quarterly reporting, you can create transportable sets for these tablespaces for storage in a tablespace repository. Subsequently, versions of the tablespace can be requested from the repository and attached to another database for use in generating reports.

Another use for transportable tablespaces is in an Oracle Streams environment. When preparing to use Oracle Streams to keep a destination database synchronized with a source database, you must perform Oracle Streams instantiation. You must bring the destination database up to a given SCN at which the two databases were known to be synchronized before you can actually use Oracle Streams to move subsequent updates from the source database to the destination database. You can create transportable tablespace sets from backups as part of the Oracle Streams instantiation.

A key benefit of the RMAN TRANSPORT TABLESPACE command is that it does not need access to the live datafiles from the tablespaces to be transported. In contrast, the transportable tablespace technique described in Oracle Database Administrator's Guide requires that the tablespaces to be transported are open read-only during the transport. Thus, transporting from backups improves database availability, especially for large tablespaces, because the tablespaces to be transported can remain open for writes during the operation. Also, placing a tablespace in read-only mode can take a long time, depending on current database activity.

The RMAN TRANSPORT TABLESPACE command also enables you to specify a target point in time, SCN, or restore point during your recovery window and transport tablespace data as it existed at that time (see "Creating a Transportable Tablespace Set at a Specified Time or SCN"). For example, if your backup retention policy guarantees a one week recovery window, and if you want to create transportable tablespaces based on the contents of the database on the last day of the month, then RMAN can perform this task at any time during the first week of the next month.

Basic Concepts of Transportable Tablespace Sets

You create a transportable tablespace set by connecting RMAN to a source database as TARGET and then executing the TRANSPORT TABLESPACE command. The source database contains the tablespaces to be transported.

You must have a backup of all needed tablespaces and archived redo log files available for use by RMAN that can be recovered to the target point in time for the TRANSPORT TABLESPACE operation. Figure 25-1 illustrates the basic process of transportable tablespace creation.

Figure 25-1 RMAN Transportable Tablespace From Backup: Architecture

Description of "Figure 25-1 RMAN Transportable Tablespace From Backup: Architecture"

The process shown in Figure 25-1 occurs in the following phases:

1. RMAN starts an auxiliary instance.

   An auxiliary instance is created by RMAN on the same host as the source database to perform the restore and recovery of the tablespaces. RMAN automatically creates an initialization parameter file for the auxiliary instance and starts it NOMOUNT.

2. RMAN restores a backup of the source database control file to serve as the auxiliary instance control file and mounts this control file.

3. RMAN restores auxiliary set and transportable set datafiles from the backups of the source database.

   The auxiliary set includes datafiles and other files required for the tablespace transport but which are not themselves part of the transportable tablespace set. The auxiliary set typically includes the SYSTEM and SYSAUX tablespaces, tempfiles, and datafiles containing rollback or undo segments. The auxiliary instance has other files associated with it, such as its own control file, parameter file, and online logs, but they are not part of the auxiliary set.

   RMAN stores the auxiliary datafiles in the selected auxiliary destination. The auxiliary destination is a disk location where RMAN can store auxiliary set files such as the parameter file, datafiles (other than those in the transportable set), control files, and online logs of the auxiliary instance during the transport. If the transport succeeds, then RMAN deletes these files.

   RMAN stores the transportable set files in the tablespace destination. The tablespace destination is a disk location that by default contains the datafile copies and other output files when the tablespace transport command completes.

4. RMAN performs database point-in-time recovery (DBPITR) at the auxiliary instance.

   The recovery updates auxiliary and transportable set datafiles to their contents as of the target time specified for the TRANSPORT TABLESPACE command. If no target time is specified, then RMAN recovers with all available redo. RMAN restores archived redo logs from backup as necessary at the auxiliary destination (or other location) and deletes them after they are applied.

5. RMAN opens the auxiliary database with the RESETLOGS options.

   The datafiles now reflect the tablespace contents as of the target SCN for the tablespace transport operation.

6. RMAN places the transportable set tablespaces of the auxiliary instance into read-only mode. RMAN also invokes Data Pump Export in transportable tablespace mode to create the export dump file for the transportable set.

   By default, the dump file is located in the tablespace destination. To specify the dump file location, see "Specifying Locations for Data Pump Files".

   RMAN also generates the sample Data Pump import script for use when plugging in the transported tablespaces at a target database. The contents of this script are written to a file named impscript.sql in the tablespace destination. The commands for the script are also included in the RMAN command output.

7. If the preceding steps are successful, then RMAN shuts down the auxiliary instance and deletes all files created during TRANSPORT TABLESPACE except for the transportable set files, the Data Pump Export file, and the sample import script.

Basic Steps of Creating Transportable Tablespace Sets

Before creating transportable tablespace sets you must meet a number of prerequisites. These prerequisites are described in the TRANSPORT TABLESPACE entry in Oracle Database Backup and Recovery Reference.

The basic steps are as follows:

1. Start the RMAN client and connect to the source database and, if used, the recovery catalog.

2. If necessary, set additional parameters in the auxiliary instance parameter file.

   This task is described in "Customizing Initialization Parameters for the Auxiliary Instance".

3. Execute the TRANSPORT TABLESPACE command.

   This basic technique is described in "Creating a Transportable Tablespace Set". Variations on this technique are described in "Transportable Tablespace Set Scenarios".

4. If the TRANSPORT TABLESPACE command fails, troubleshoot the problem and then retry the command until it succeeds.

   This technique is described in "Troubleshooting Creation of Transportable Tablespace Sets".

5. Return to the procedure for transporting tablespaces described in Oracle Database Administrator's Guide.

Setting Initialization Parameters for the Auxiliary Instance

RMAN defines the basic initialization parameters in Table 25-1 for the automatic auxiliary instance.

Overriding one of the basic initialization parameters in Table 25-1 with an inappropriate value in the auxiliary instance parameter file can cause TRANSPORT TABLESPACE to fail. If you encounter a problem, then try returning the initialization parameter to its default value.

Setting the Location of the Auxiliary Instance Parameter File

By default, RMAN looks for the auxiliary initialization parameter file at an operating system-dependent location on the host running the RMAN client. This location may not be on the host running the auxiliary instance. For UNIX systems, this location is ?/rdbms/admin/params_auxint.ora, where question mark (?) stands for ORACLE_HOME on the host running RMAN. If no file is found in the default location, then RMAN does not generate an error.

If you use the default initialization parameters for the auxiliary instance, then check whether an auxiliary instance parameter file exists before running TRANSPORT TABLESPACE.

You can use the RMAN SET AUXILIARY INSTANCE PARAMETER FILE command in a RUN block before TRANSPORT TABLESPACE to specify a different location for the auxiliary instance parameter file. As with the default location of the auxiliary instance parameter file, the path specified when using SET AUXILIARY INSTANCE PARAMETER FILE is a client-side path.

Assume you create a file named /tmp/auxinstparams.ora on the host running the RMAN client. This file contains the following initialization parameter:

SHARED_POOL_SIZE=150M;

You can then use the initialization parameter file with TRANSPORT TABLESPACE as shown in Example 25-1. The SHARED_POOL_SIZE parameter in /tmp/auxinstparams.ora overrides the default value used for SHARED_POOL_SIZE when RMAN creates the auxiliary instance.

RUN
{
  SET AUXILIARY INSTANCE PARAMETER FILE TO '/tmp/auxinstparams.ora';
  TRANSPORT TABLESPACE tbs_2 
    TABLESPACE DESTINATION '/disk1/transportdest' 
    AUXILIARY DESTINATION '/disk1/auxdest';
}

Creating a Transportable Tablespace Set at a Specified Time or SCN

You can specify a target time or SCN with the TRANSPORT TABLESPACE command. During the tablespace transport operation, RMAN restores the tablespace at the auxiliary instance with backups from before the target time and performs point-in-time recovery on the auxiliary database to the specified target time. Backups and archived redo logs needed for this point-in-time recovery must be available.

You can specify the target time with an SCN (in the current incarnation or its ancestors) as shown in Example 25-3.

TRANSPORT TABLESPACE tbs_2 
   TABLESPACE DESTINATION '/disk1/transportdest' 
   AUXILIARY DESTINATION '/disk1/auxdest'
   UNTIL SCN 11379;

You can also specify a restore point as shown in Example 25-4.

TRANSPORT TABLESPACE tbs_2 
   TABLESPACE DESTINATION '/disk1/transportdest' 
   AUXILIARY DESTINATION '/disk1/auxdest'
   TO RESTORE POINT 'before_upgrade';

You can also specify an end time as shown in Example 25-5.

TRANSPORT TABLESPACE tbs_2 
   TABLESPACE DESTINATION '/disk1/transportdest' 
   AUXILIARY DESTINATION '/disk1/auxdest'
   UNTIL TIME 'SYSDATE-1';

Specifying Locations for Data Pump Files

You can change the names of the Data Pump Export dump file for the transportable set, the sample import script for use at the target database, the log file generated by Data Pump Export, and the directory to which they are written.

By default, these files are stored in the tablespace destination and named as follows:

• The Data Pump Export dump file is named dmpfile.dmp.

• The export log file is named explog.log.

• The sample import script is named impscrpt.sql.

You can place the dump file and the export log in a different directory by using the DATAPUMP DIRECTORY clause, passing in the name of a database directory object. The database directory object used by DATAPUMP DIRECTORY is not the directory path of an actual file system directory. The value passed corresponds to the DIRECTORY command line argument of Data Pump Export. See Oracle Database Utilities for more details on the use of directory objects with Data Pump Export.

You can rename these files with the DUMP FILE, EXPORT LOG, and IMPORT SCRIPT clauses of TRANSPORT TABLESPACE. The filenames cannot contain full file paths with directory names. If the DUMP FILE or EXPORT LOG filenames specify file paths, then TRANSPORT TABLESPACE fails when it attempts to generate the export dump files. Use the DATAPUMP DIRECTORY clause to specify a database directory object that identifies a location for the outputs of Data Pump Export.

The following scenario illustrates the use of TRANSPORT TABLESPACE with the DATAPUMP DIRECTORY, DUMP FILE, EXPORT LOG and IMPORT SCRIPT filenames specified. Assume that you create a database directory object as follows for use with Data Pump Export:

CREATE OR REPLACE DIRECTORY mypumpdir as '/datapumpdest';

Example 25-6 shows a TRANSPORT TABLESPACE command with optional arguments that specify output file locations.

TRANSPORT TABLESPACE tbs_2
   TABLESPACE DESTINATION '/transportdest'
   AUXILIARY DESTINATION '/auxdest'
   DATAPUMP DIRECTORY  mypumpdir
   DUMP FILE 'mydumpfile.dmp'
   IMPORT SCRIPT 'myimportscript.sql'
   EXPORT LOG 'myexportlog.log';
   

After a successful run, RMAN cleans up the auxiliary destination, creates the Data Pump Export Dump file and the export log in the directory referenced by DATAPUMP DIRECTORY (/datapumpdest/mydumpfile.dmp and /datapumpdest/myexportlog.log), and stores the transportable set datafiles in /transportdest.

Specifying Auxiliary File Locations

Several rules affect the location of auxiliary instance files created during the transport.

If RMAN determines that any of the auxiliary files, designated by any of the methods for specifying auxiliary file locations, already contain a datafile copy that is suitable to be used for the desired point in time for this transport operation, then that datafile copy will be used instead of restoring the datafile.

Any datafile copies that are present, but not suitable for this transport operation, because they are more recent than the requested point in time, or are not recognized as part of the target database, are overwritten when the datafiles are restored.

The simplest technique is to use AUXILIARY DESTINATION and let RMAN manage all file locations automatically. To relocate some or all auxiliary instance files, the following options for specifying file locations appear in order of precedence:

1. SET NEWNAME FOR DATAFILES

   SET NEWNAME FOR TABLESPACE

   SET NEWNAME FOR DATABASE

   As described in "Using SET NEWNAME for Auxiliary Datafiles".

2. CONFIGURE AUXNAME

   As described in "Using CONFIGURE AUXNAME for Auxiliary Datafiles", you can use this command to specify names for datafiles.

3. AUXILIARY DESTINATION

   As described in "Using AUXILIARY DESTINATION to Specify a Location for Auxiliary Files", you can use this command to specify a location for auxiliary files.

4. LOG_FILE_NAME_CONVERT and DB_FILE_NAME_CONVERT in the initialization parameter file

   As described in "Using Initialization Parameters to Name Auxiliary Files", you can use this command to specify a location for auxiliary files.

If you use several rules, then the first rule in the list that applies to a file determines the filename.

RUN
{
  SET NEWNAME FOR DATAFILE '/oracle/dbs/tbs_12.f' 
    TO '/bigdrive/auxdest/tbs_12.f';
  SET NEWNAME FOR DATAFILE '/oracle/dbs/tbs_11.f'
    TO '/bigdrive/auxdest/tbs_11.f';
  TRANSPORT TABLESPACE tbs_2 
    TABLESPACE DESTINATION '/disk1/transportdest' 
    AUXILIARY DESTINATION '/disk1/auxdest';
}