Dropping redo log Files

You can use theALTER DATABASE command to drop log file groups or individual members from your database.
The following syntax shows the syntax for both 1) dropping a group and 2) dropping a member:

ALTER DATABASE
DROP LOGFILE (GROUP group_number)
DROP LOGFILE 'existing_filename';
DROP LOGFILE ('existing_filename', 'existing_filename'...);
ALTER DATABASE
DROP LOGFILE MEMBER 'filename', 'filename'...;

Description of the Commands:

1. Command Structure: These commands are used for altering the database configuration by removing log files and log file members, which are essential for controlling the logging and recovery mechanisms in a database.
2. Command Keywords:
   • ALTER DATABASE: This initiates a command to modify the database.
   • DROP LOGFILE: This clause is used to remove one or more log files.
   • DROP LOGFILE MEMBER: This clause is specifically used to remove log file members from their respective groups.
3. Parameters:
   • GROUP group_number: Specifies the log file group from which log files should be removed.
   • existing_filename: Lists the specific log files to be dropped by name.
   • filename: Lists the specific log file members to be removed.

These commands would typically be used in situations where a database administrator needs to manage the space or reconfigure the settings associated with logging. This might be due to log files growing too large, changing storage strategies, or troubleshooting issues with log files in systems such as Oracle, SQL Server, or other relational databases that utilize structured logging. drop Logfile

1. The command to use.
2. The clause that drops a log file group.
3. The clause that drops an individual log file.
4. Identifies the log file group to drop.
5. You may optionally identify the log file group to drop by naming its member files. If there is only one member filename, this is how you specify it
6. If you are dropping a group with multiple files, you can identify it by listing all the filenames.
7. When dropping individual log files, you identify the files by name. Oracle determines for itself to which group each file belongs.

ALTER DATABASE	The command to use.
DROP LOGFILE	The clause that drops a log file group.
DROP LOGFILE MEMBER	The clause that drops an individual log file.
GROUP group_number	Identifies the log file group to drop.
'existing_filename'	You may optionally identify the log file group to drop by naming its member files. If there is only one member filename, this is how you specify it.
('existing_filename', 'existing_filename'...)	If you are dropping a group with multiple files, you can identify it by listing all the filenames.
'filename'	When dropping individual log files, you identify the files by name. Oracle determines for itself to which group each file belongs.

Caveats when dropping redo log files
There are a few caveats to remember when dropping redo log files:

1. Oracle won't allow you to drop the currently active redo log group.
2. Oracle won't allow you to drop a redo log group that needs to be archived.
3. Oracle requires that you have at least two groups at all times.
4. TheDROP LOGFILE MEMBER clause cannot be used to drop all log files in a group. For that, you must useDROP LOGFILE.

If you are trying to drop a group and you suspect that it might be the active group, you can query the v$log view to make certain that's the case. v$log will return one row for each redo log group and will identify the current group by returning a value ofCURRENT in the status column for that group. You can force a log switch using theALTER SYSTEM command, which you will learn to do later in this module. In the next lesson, you will learn a couple of approaches to moving redo log files.