Performing Oracle User-Managed Database Recoveries - OCP: Oracle Database 12c Administrator Certified Professional - page 90

Recovering from Loss of All Control Files
If you lose your control files, Oracle is not shy about telling you. If you are trying to start
up your database and your control files are missing, you will see an error like this:
SQL> startup
ORACLE instance started.
Total System Global Area 171581440 bytes
Fixed Size 1298640 bytes
Variable Size 146804528 bytes
Database Buffers 20971520 bytes
Redo Buffers 2506752 bytes
ORA-00205: error in identifying control file, check alert log for more info
This error will occur on startup if any of your control files are missing. If your database is
running, the loss of some of your control files will not cause it to stop operating. As a result,
you can plan to shut down your database and then simply copy a surviving copy of the con-
trol file to the location of the lost control file. If the location is no longer available, you can
modify the CONTROL_FILES parameter so that it points to the location of the new control file.
If you lose your control files while the database is running, it is quite likely that the
database will crash in short order. There are some cases where it might stay up for a little
while, but it will eventually come down on you.
Loss of all control files will require that you use a backup control file or issue the CREATE
CONTROLFILE command from the SQL prompt. We discussed the creation of a backup control
file in Chapter 1. We also discussed how to create a trace file with the CREATE CONTROLFILE
command in it in Chapter 1. Let's look at each of these recoveries in a bit more detail.
Recovering Lost Control Files with a Backup Control File
If you have a backup control file, follow these steps to recover from the loss of all your
control files:
1. Copy the backup control file to the location of each control file defined by the parameter
CONTROL_FILES .
2. Modify the CONTROL_FILES parameter if required.
3. Mount the database with the STARTUP MOUNT command.
4. Recover the database using the RECOVER DATABASE USING BACKUP CONTROLFILE
command.
5. At the prompt, type in AUTO to apply all archived redo logs.
Recovery will end, likely with an error. This is because the final redo log sequence num-
ber you need to apply is not in an archived redo log but is in one of the online redo logs.
6. Issue the RECOVER DATABASE USING BACKUP CONTROLFILE command again. This time,
when prompted for the archived redo log to apply, enter one of your online redo log
names (for example, redo01.log ).