ASM file number 8


The disk Used Space Directory (USD) – ASM file number 8 - maintains the number of allocation units (AU) used per zone, per disk in a disk group. The USD is split into a set of Used Space Entries (USE). Each USE will maintain a counter for the number of used AUs per disk, per zone. A disk zone can be either HOT or COLD.

This structure is version 11.2 specific and is relevant to the Intelligent Data Placement feature. The USD will be present in a newly created disk group in version 11.2 or when the ASM (more...)

ASM file number 7


ASM metadata file number 7 - volume directory - keeps track of files associated with ASM Dynamic Volume Manager (ADVM) volumes.

An ADVM volume device is constructed from an ASM dynamic volume. One or more ADVM volume devices may be configured within each disk group. ASM Cluster File System (ACFS) is layered on ASM through the ADVM interface. ASM dynamic volume manager is another client of ASM - the same way the database is. When a volume is opened, the corresponding ASM file is opened and ASM extents are sent to the ADVM driver.

There are two file types associated (more...)

ASM file number 6


The alias directory - ASM file number 6 - provides a hierarchical  naming system for all the files in a disk group.

A system file name is created for every file and it is based on the file type, database instance and type-specific information such as tablespace name. User alias may also be created if a full path name was given when the file was created.

Alias Directory entries include the following fields:
  • Alias or directory name
  • Alias incarnation number
  • File number
  • File incarnation number
  • Parent directory
  • System flag
The ASM alias information is externalised via V$ASM_ALIAS view.

Using the alias

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ASM file number 5


The Template Directory - ASM file number 5 - contains information about all file templates for the disk group.

There are two types of templates - system and user created. The default (system) templates are always available for each file type supported by ASM. User created templates can be added for a custom template specifications.

Each template entry contains the following information:
  • The template name (for the default templates this corresponds to the file type)
  • The file redundancy (defaults to the disk group redundancy)
  • The file striping (default is file-type specific)
  • The system flag (set for the system templates)
Using (more...)

ASM file number 4


Some long-running ASM operations, like rebalance, drop disk, create/delete/resize file, cannot be described by a single record in the active change directory. For those operations ASM uses the Continuing Operations Directory (COD) - ASM file number 4. There is one COD per disk group.

If a process performing the long-running operation dies before completing it, a recovery process will look at the entry and either complete or rollback the operation. There are two types of continuing operations - background and rollback.

Background operation

A background operation is preformed by an ASM instance background process. It is done as part of (more...)