Considerations for standby databases using ASM

Considerations for Standby Databases using Automatic Storage Management

Every file created in ASM gets a system-generated filename, otherwise known as a fully qualified filename (FQFN). The fully qualified filename represents a complete pathname in the ASM file system. An example of a fully qualified filename is:

+dgroup2/sample/controlfile/Current.256.541956473

You can use the fully qualified filename to reference (read or retrieve) an ASM file. ASM generates a fully qualified filename upon any request to create a file. A creation request cannot specify a fully qualified filename. Instead, it uses a simpler syntax to specify a file, such as an alias or just a disk group name. ASM then creates the file, placing it in the correct ASM "path" according to file type, and then assigns an appropriate fully qualified filename. If you specify an alias in the creation request, ASM also creates the alias so that it references the fully qualified filename.

FQFN are generally long and awkward, therefore, to make file-naming convention easier to remember the ASM Alias name format was introduced. ASM Aliases are essentially in hierarchical directory format, similar to the filesystem hierarchy. Alias names specify a disk group name, but instead of a file and incarnation number, a user-friendly string name is used.

Alias ASM filenames, otherwise known as aliases, can be used both for referencing existing ASM files and for creating new ASM files. Alias names start with the disk group name preceded by a plus sign, after which you specify a name string of your choosing. Alias filenames are implemented using a hierarchical directory structure, with the slash (/) or backslash (\) character separating name components. You can create an alias in any system-generated or user-created ASM directory. You cannot create an alias at the root level (+), however.

When you create an ASM file with an alias filename, the file is created with a fully qualified name, and the alias filename is additionally created. You can then access the file with either name.

Alias ASM filenames are distinguished from fully qualified or numeric names because they do not end in a dotted pair of numbers. An example of ASM alias for the fully qualified filename above is:

+ dgroup2/sample/controlfile/control01.dbf