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Don Burleson Blog 







How to remove a database instance

Oracle Database Tips by Donald BurlesonDecember 14,  2015


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
/oracle0/data/                      Place instance names under type directories
                                  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


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.



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




/var/opt/oracle/oratab (Solaris)


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



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



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.





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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