Among other things, it
contains the name of the database, when the database was created, and the names and locations
of all datafiles and redo log files. In addition, the control file maintains information used by
Recovery Manager (RMAN), such as the persistent RMAN settings and the types of backups
that have been performed on the database. RMAN is covered in depth in Chapter 12. Whenever
any changes are made to the structure of the database, the information about the changes is
immediately reflected in the control file.
Chapter 1: Getting Started with the Oracle Architecture 27
Because the control file is so critical to the operation of the database, it can also be multiplexed.
However, no matter how many copies of the control file are associated with an instance, only one
of the control files is designated as primary for purposes of retrieving database metadata.
The alter database backup controlfile to trace command is another way to back up the
control file. It produces a SQL script that you can use to re-create the database control file in
case all multiplexed binary versions of the control file are lost due to a catastrophic failure.
This trace file can also be used, for example, to re-create a control file if the database needs
to be renamed, or to change various database limits that could not otherwise be changed without
re-creating the entire database.
Archived Log Files
An Oracle database can operate in one of two modes: archivelog or noarchivelog mode.
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