= Using the NIF database back-end =

Currently, the Mnesia based back-end is the default,
therefore you have to specify a command line argument if you would like to use the NIF based back-end.

After the system is installed, start !RefactorErl with
{{{
#!sh

bin/referl -db nif
}}}

NIF uses the !RefactorErl data directory to store its data. You can specify it by typing
{{{
#!sh

bin/referl -db nif -dir /path/to/your/data/dir
}}}

If you would like to start several instances of !RefactorErl/NIF,
you have to choose different node names.
It is also suggested to set different data directories as well,
although it is not strictly required.
{{{
#!sh

bin/referl -db nif -sname name1 -dir /path/to/your/data/dir1
bin/referl -db nif -sname name2 -dir /path/to/your/data/dir2

# or

bin/referl -db nif -name name1 -dir /path/to/your/data/dir1
bin/referl -db nif -name name2 -dir /path/to/your/data/dir2
}}}

After the system is started, the following operations work on the full database.

{{{
% Clear the whole database.
ri:reset().

% Make a checkpoint.
% This operation is always executed after transformations
% and file operations (e.g. adding or dropping a file).
ri:backup().

% After that the output will be
{ok, backup.1}
% This backup will be created in the directory of the graph.

% Make a checkpoint with a commit log message.
ri:backup("Something log message").

% It will print the following:
{ok, backup.2}
% That backup.2 will be created in the same directory as backup.1.

% Now we want to know some informations about backup.2.
% Note: Here you can specify either 'backup.2' or "backup.2" or just 2. 
ri:backup_info(2).
Informations about 'backup.2':
Commit-log: Something log message
Time of creation: Tue Apr 17 11:03:29 2012

% Lists all backups.
ri:ls_backups().

% Undo all changes made since the last backup.
ri:undo().

% Removes all backups.
ri:clean().
}}}

You can also use all [[SemanticQuery|querying]] and [[RefactoringSteps|refactoring functionalities]].

= Comparison with the Mnesia back-end =

While the [[MnesiaDB|Mnesia]] back-end has been under development longer and can be expected to be more stable,
it is much slower than the NIF based back-end;
you can expect about an order of magnitude of speed-up.
Also, the NIF back-end may require less storage.
As an indication, loading ejabberd-2.1.8 (6.6 MB on disk) takes '''18323 sec''' and '''566 MB''' of RAM and '''66 MB''' of disk space, while the NIF back-end on the same machine takes '''458 sec''' and '''556 MB''' of RAM and '''52 MB''' of disk space.