DBA Tips Archive for Oracle
How Change DB_NAME & ORACLE_SID
by Jeff Hunter, Sr. Database Administrator
This month, I will describes how to find and change the "db_name" for a database, or the ORACLE_SID for an instance, without recreating the database.
Query the data dictionary to find the current DB_NAME and ORACLE_SID
Query the views v$database and v$thread.
ORACLE_SID = DB_SID and db_name = DBNAME:
- V$DATABASE gives DB_NAME
- V$THREAD gives ORACLE_SID
To find the current value of ORACLE_SID:SVRMGR> select instance from v$thread; INSTANCE ---------------- DB_SIDTo find the current value of DB_NAME:SVRMGR> select name from v$database; NAME --------- DBNAME
How to modify the database to run under a new ORACLE_SID
1. Shutdown the instance 2. Backup all control, redo, and data files. 3. Go through the .profile, .cshrc, .login, oratab, tnsnames.ora, (for SQL*Net version 2), and redefine the ORACLE_SID environment variable to a new value. For example, search through disks and do a grep ORACLE_SID * 4. Change locations to the "dbs" directory % cd $ORACLE_HOME/dbs and rename the following files: o init
.ora (or use pfile to point to the init file.) o control file(s). This is optional if you do not rename any of the controlfiles, and the control_files parameter is used. The "control_files" parameter is set in the "init .ora" file or in a file it references with the ifile parameter. Make sure that the control_files parameter does not point to old file names, if you have renamed them. o "crdb .sql" & "crdb2 .sql", This is optional. These are only used at database creation. 5. Change locations to the "rdbms/admin" directory % cd $ORACLE_HOME/rdbms/admin and rename the file: o startup .sql. This is optional. On some platforms, this file may be in the "$ORACLE_HOME/rdbms/install" directory. Make sure that the contents of this file do not reference old init .ora files that have been renamed. This file simplifies the "startup exclusive" process to start your database. 6. To rename the database files and redo log files, you would follow the instructions in [NOTE:9560.1]. 7. Change the ORACLE_SID environment variable to the new value. 8. Check in the "$ORACLE_HOME/dbs" directory to see if the password file has been enabled. If enabled, the file "orapw " will exist and a new password file for the new SID must be created (renaming the old file will not work). If "orapw " does not exist, skip to step 9. To create a new password file, issue the following command as oracle owner: orapwd file=orapw password=?? entries= 9. Start up the database and verify that it works. Once you have done this, shutdown the database and take a final backup of all control, redo, and data files. 10. When the instance is started, the control file is updated with the current ORACLE_SID.
How to the "db_name" for a Database
1. Login to Server Manager % svrmgrl SVRMGR> connect internal 2. Type SVRMGR> alter system switch logfile; to force a checkpoint. 3. Type SVRMGR> alter database backup controlfile to trace resetlogs; This will create a trace file containing the "CREATE CONTROLFILE" command to recreate the controlfile in its current form. 4. Shutdown the database and exit SVRMGR SVRMGR> shutdown SVRMGR> exit The database must be shutdown with SHUTDOWN NORMAL or SHUTDOWN IMMEDIATE. It must not be shutdown abnormally using SHUTDOWN ABORT. 5. Change locations to the directory where your trace files are located. They are usually in the "$ORACLE_HOME/rdbms/log" directory. If "user_dump_dest" is set in the "init
.ora" file, then go to the directory listed in the "user_dump_dest" variable. The trace file will have the form "ora_NNNN.trc with NNNN being a number. 6. Copy the contents of the trace file starting from the line with STARTUP NOMOUNT down to the end of the trace file and put it in a new file called something like "ccf.sql". 7. Edit the "ccf.sql" file FROM: CREATE CONTROLFILE REUSE DATABASE "olddbname" RESETLOGS ... TO: CREATE CONTROLFILE set DATABASE "newdbname" RESETLOGS ... Change the word 'REUSE' to 'set' and the 'olddbname' to 'newdbname'. It is possible to recreate the controlfile using the syntax: CREATE CONTROLFILE REUSE set DATABASE "newdbname" RESETLOGS ... But this syntax will allow the existing controlfiles to be overwritten without giving an error. FROM: # Recovery is required if any of the datafiles are restored backups, # or if the last shutdown was not normal or immediate. RECOVER DATABASE USING BACKUP CONTROLFILE TO: # Recovery is required if any of the datafiles are restored backups, # or if the last shutdown was not normal or immediate. # RECOVER DATABASE USING BACKUP CONTROLFILE The last command in ccf.sql should be: alter database open resetlogs 8. Save and exit the "ccf.sql" file 9. Rename the old control files for backup purposes and so that they do not exist when creating the new ones. 10. Edit the "init .ora" file so that db_name="newdb_name" . 11. Login to Server Manager % svrmgrl SVRMGR> connect internal 12. Run the "ccf.sql" script SVRMGR> @ccf This will issue a startup nomount, and then recreate the controlfile. If, at this point, you receive the error that a file needs media recovery, the database was not shutdown normally as specified in step 4. You can try recovering the database using the redo in the current logfile, by issuing: SVRMGRL> recover database using backup controlfile until cancel; This will prompt for an archived redologfile. It may be possible to open the database after applying the current logfile. BUT this is not guaranteed. To apply the necessary redo, you need to check the online logfiles and apply the one with the same sequence number as reported in the message. This usually is the logfile with status=CURRENT. If not apply, the logfiles in turn until the logfile with status=CURRENT has been applied. If, after applying the current logfile, the database will not open then it is highly likely that the operation must be restarted having shutdown the database normally. To find a list of the online logfiles: SVRMGR> select group#, seq#, status from v$log; GROUP# SEQUENCE# STATUS ---------- --------- ---------------- 1 123 CURRENT <== this redo needs to be applied 2 124 INACTIVE 3 125 INACTIVE 4 126 INACTIVE 5 127 INACTIVE 6 128 INACTIVE 7 129 INACTIVE 7 rows selected. SVRMGR> select member from v$logfile where GROUP# = 1; Member ------------------------------------ /u02/oradata/V815/redoV81501.log After applying the current online log file the following prompt should be displayed: Log Applied Media Recovery Complete At this point the database can be opened with: SVRMGR> alter database open resetlogs; 13. You may also need to change the global database name: alter database rename global_name to . 14. Make sure the database is working. 15. Shutdown and backup the database.
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