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Oracle DBA Pocket Guide
WARNING
Although the SPFILE looks like a plain text file, it is very
important to realize that the SPFILE must not be edited
directly. If you edit your SPFILE (with a text editor, for ex-
ample), then the next attempt to start your database will
result in a failure. You will be unable to start your data-
base unless you have created a backup INIT.ORA file
(which is a good practice for just this reason).
Dynamic and Static Parameters
While most initialization parameters are static, taking their
values from the initialization file as it exists at the time of
database startup, some may be dynamically modified while
the instance is up and the database is open.
Dynamic modification is different from dynamic storage of a
changed value in the SPFILE. In all versions of Oracle, you
can dynamically modify a setting using the ALTER SYSTEM
or ALTER SESSION command. These changes may also be
dynamically stored in the SPFILE, depending on the value of
the SCOPE clause of the ALTER command.
NOTE
Remember that if you use an INIT.ORA file, dynamic
changes to parameters will never be saved to it; you must
edit the INIT.ORA file yourself (or recreate it from the
SPFILE).
Backup and Recovery
Even with redundant hardware, you will still need to back up
your database. You can do this through a logical backup
(export) or a physical backup at the datafile level. As you’d
expect, there are trade-offs