Fully Qualified Names
Fully qualified ASM filenames are used only when referencing an existing file. A fully qualified
ASM filename has the format
+group/dbname/file type/tag.file.incarnation
where group is the disk group name, dbname is the database to which the file belongs, file type is
the Oracle file type, tag is information specific to the file type, and the file.incarnation pair ensures
uniqueness. Here is an example of an ASM file for the USERS tablespace:
+DATA/dw/datafile/users.259.627432977
The disk group name is +DATA, the database name is dw, it??™s a datafile for the USERS
tablespace, and the file number/incarnation pair 259.627432977 ensures uniqueness if you
decide to create another ASM datafile for the USERS tablespace.
Numeric Names
Numeric names are used only when referencing an existing ASM file. This allows you to refer
to an existing ASM file by only the disk group name and the file number/incarnation pair. The
numeric name for the ASM file in the preceding section is
+DATA.259.627432977
Alias Names
An alias can be used when either referencing an existing object or creating a single ASM file.
Using the alter diskgroup add alias command, a more readable name can be created for an
existing or a new ASM file, and it??™s distinguishable from a regular ASM filename because it
does not end in a dotted pair of numbers (the file number/incarnation pair), as shown here:
Chapter 4: Physical Database Layouts and Storage Management 105
SQL> alter diskgroup data
2 add directory '+data/purch';
Diskgroup altered.
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