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How to remove a database instance

Oracle Tips by Burleson Consulting
December 14,  2008

 

Question:  I need to understand how to remove a database instance from my server.  I have moved it to a new server and I now need to remove the instance.  I can find no documentation for this.  What are the procedures for deleting a database instance from the server?

Answer:  An Oracle instance consists of these components:

  • The database files (*.dbf and *.ctl)
  • The database file system ($ORACLE_HOME/admin/$ORACLE_SID) directories.  These contain the bdump, cdump, arch and pfile.
  • The OS control structures.  In Windows these exist in the registry, while in UNIX/Linux they exist in directories such as /etc and /var/opt/oracle
  • The OS user ID's.  These include the "oracle" user who owns the OS files.
  • The Oracle software.  This exists in the $ORACLE_HOME/bin location.

To remove an instance in Windows:

  1. Shutdown and archive and/or backup the database
  2. Remove all Oracle .dbf and .ctl files
  3. Remove all Oracle directories
  4. Remove all Oracle registry entries
  5. Remove the oracle user

To remove a database instance in UNIX/Linux:

  1. Shutdown and archive and/or backup the database
  2. Remove all Oracle .dbf and .ctl files
  3. Remove all Oracle directories
  4. Remove all Oracle external files (/etc/oratab, /var/opt/oracle/oratab)
  5. Remove the oracle user (/etc/passwd and /etc/group)

Up to Oracle 10g, the file structure should look like the following:

/oracle0/product/oracle/8.1.3/            Top level $ORACLE_HOME
                                              bin/                  Standard distribution
structure under version
                                              doc/  
                                               rdbms/
                                               …
/oracle0/data/                      Place instance names under type directories
                     ortest1/
                     ortest2/
/oracle0/control/
                     ortest1/
                     ortest2/
/oracle0/redo/
                     ortest1/
                     ortest1/
/oracle0/admin/
                     ortest1/
                                  bdump/        backup_dump_dest
                                  udump/        user_dump_dest
                                  cdump/        core_dump_dest
                                  pfile/        initialization file location (linked
back to dbs directory)
                                  create/             Database creation script storage area
                     ortest2/
                                …
/oracle1/data/
            /control/
            /redo/
/oracle2/data/ 
            /control/
            /redo/

/oracle7/data/
            /control/
            /redo/

In Oracle 11g, the file directories have changed.

  • The new $ADR_HOME directory is located by default at $ORACLE_BASE/diag, with the directories for each instance at $ORACLE_HOME/diag/$ORACLE_SID, at the same level as the traditional bdump, udump and cdump directories and the initialization parameters background_dump_dest and user_dump_dest are deprecated in 11g.

  • In 11g, each $ORACLE_HOME/diag/$ORACLE_SID directory may contain these new directories:

    • alert - A new alert directory for the plain text and XML versions of the alert log.
       

    • incident - A new directory for the incident packaging software.
       

    • incpkg - A directory for packaging an incident into a bundle.
       

    • trace - A replacement for the ancient background dump (bdump) and user dump (udump) destinations.
       

    • cdump - The old core dump directory retains it's 10g name.

In Windows, these are the registry entries.  See MOSC notes 124353.1 and 208256.1 to clean the registry.

HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\ALL_HOMES\IDx

HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_ora10g_Home1
HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_ora10g_Home2

In UNIX/Linux, these are the external Oracle files:

PATH AND FILE

DESCRIPTION

/etc/oratab 

/var/opt/oracle/oratab (Solaris)

    

The oratab file is used to identify each SID with its associated ORACLE_HOME.

/var/opt/oracle/srvConfig.loc

/etc/oracle/ocr.loc

This is a text file that identifies the location of the file used for cluster configuration and srvctl repository.

/etc/oraInst.loc

 

Identifies the location on disk of the Oracle inventory files and identifies the OS user group that owns the Oracle install. For a 10g install, this file is located in the $ORACLE_HOME directory.

/usr/local/bin/oraenv

/usr/local/bin/racenv

/usr/local/bin/coraenv

/usr/local/bin/dbhome

These scripts are used to set environmental variables. The oraenv and racenv scripts are Bash shell scripts used extensively in this book. The coraenv script is used in the C shell. The dbhome script is used by the other three scripts to identify the home directory associated with given database.

 

 

 


 

 

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