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Downgrading to Oracle7

The information in this chapter only applies to release 8.0 and higher installations of Oracle. The term downgrading describes transforming an Oracle database into a previous release of the same version, such as transforming a database from release 8.1 to release 8.0. The term downgrading also describes transforming an Oracle database into a previous version, such as transforming a database from Oracle8i to Oracle7.

This chapter describes downgrading to Oracle7. If you want to downgrade to a previous 8.0 or 8.1 release, see Chapter 12.

This chapter covers the following topics:

• Overview of Downgrading from Oracle8i to Oracle7

• Downgrading a Database That Does Not Contain New or Changed Data

• Downgrading a Database That Contains New or Changed Data

  See Also: Some aspects of downgrading are operating-system specific. See your operating-system specific Oracle documentation for additional instructions about downgrading.

Overview of Downgrading from Oracle8i to Oracle7

An Oracle8i database can be downgraded to an Oracle7 database (such as release 7.3). However, few downgrade paths are available, and the necessary procedures may require a great deal of time and effort. Also, it may not be possible to preserve data that uses new version 8 features that are not available with Oracle7.

Oracle does not support downgrading from Oracle8i to Oracle7 using the Oracle8i Migration utility; in other words, the Oracle8i Migration utility does not support backward migration. Oracle8i provides no other facilities specifically for downgrading.

The procedure for downgrading depends on whether the Oracle8i database contains new or changed data that must be preserved. Use the procedure that applies to your Oracle8i database:

• Downgrading a Database That Does Not Contain New or Changed Data

• Downgrading a Database That Contains New or Changed Data

Downgrading a Database That Does Not Contain New or Changed Data

If the Oracle8i database contains no new or changed data that must be preserved, simply restore the complete backup of the previous Oracle7 source database and open it again. Make sure the restore includes the initialization parameters that were used in the previous Oracle7 database.

See Also: Oracle7 Server Administrator's Guide for more information about restoring a backed up Oracle7 database.

Any new or changed data in the release 8.1 database is lost when you use the method described in the previous paragraph. If your release 8.1 database has new or changed data that must be preserved, use the procedure described in "Downgrading a Database That Contains New or Changed Data".

Downgrading a Database That Contains New or Changed Data

If the Oracle8i database contains new or changed data that must be preserved, complete the procedure illustrated in Figure 13-1.

Figure 13-1 Downgrading to Oracle7

The following steps describe the procedure in more detail:

1. Run the catexp7.sql script on the Oracle8i database. This script is in the $ORACLE_HOME/rdbms/admin directory.

2. Use the Oracle7 Export utility to export the parts of the Oracle8i database containing the new or changed data.

   See Also: Oracle8i Utilities for more information about performing an Oracle7 export from an Oracle8i database.

3. Restore the complete backup of the previous Oracle7 database, and make sure the restore includes the previous initialization parameters.

   See Also: Oracle7 Server Administrator's Guide for more information about restoring a backed up Oracle7 database.

4. Open the restored Oracle7 database.

5. Use the Oracle7 Import utility to import the file previously exported from the Oracle8i database into the restored Oracle7 database.

Alternative Downgrading Methods

Several other methods are available for sending table data from the Oracle8i database back to the Oracle7 database. These methods of returning data to Oracle7 are relatively simple if only a few tables have been updated using Oracle8i. However, copying an entire database of tables can be a long and complicated task; therefore, you should decide whether you need to return to Oracle7 before you update many tables using Oracle8i.

The following alternate methods are available for downgrading an Oracle8i database to Oracle7:

• Use SQL*Plus to create non-Oracle text files from the new Oracle8i data and then use SQL*Loader to load the data back into the Oracle7 database.

• Use the SQL*Plus COPY command to copy the new data from the Oracle8i database tables into the tables in the earlier Oracle7 database.

  See Also: The SQL*Plus User's Guide and Reference for more information about the COPY command.

• If you still are running the earlier Oracle7 database, re-create the table where data has been added or changed (using CREATE TABLE ... AS SELECT). Select the data in the Oracle8i database table through a distributed query from the Oracle7 database using a database link.

  See Also: Oracle8i SQL Reference for more information on the AS clause of the CREATE TABLE command.

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