A fully-qualified file name comprises the following five components, and always ends with a special number pair:
<group>. The name of the ASM disk group.
<dbname>. The database that owns this ASM file.
<file type>. The Oracle file type (e.g. DATAFILE, ARCHIVELOG, CONTROLFILE).
<tag>. Type-specific information about the file. In this case, it is the corresponding tablespace name for the datafile.
<file>.<incarnation>. A special number pair that ASM generates to insure uniqueness.