Every time a new database is created, the database manager creates a separate directory to store the control files and data files for that database.
The naming scheme for these directories is SQL00001 through SQLnnnnn, where SQL00001 contains control files associated with the first database created, SQL00002 contains control files for the second database created, and so on.
These directories are maintained automatically. To avoid potential directory naming problems, do not create your own directories using the same naming schema as used by the database manager, and do not manipulate directories that have already been created by the database manager.