ASM files number 10 and 11

Database Management and Performance
| Jan 10, 2012

ASM metadata file number 10 is ASM user directory and ASM file number 11 is ASM group directory. These are supporting structures for ASM file access control feature.

ASM file access control can be used to restrict file access to specific ASM clients (typically databases), based on the operating system effective user identification number of a database home owner.

This information is externalized via V$ASM_USER, V$ASM_USERGROUP and V$ASM_USERGROUP_MEMBER views.

ASM users and groups

To make use of ASM file access control feature, we need to have the operating system users and groups in place. We would then add them to (more...)

ASM file number 9

Database Management and Performance
| Jan 8, 2012

The attributes directory - ASM file number 9 - contains metadata about disk group attributes. The attributes directory exists only in disk groups where COMPATIBLE.ASM is 11.1 or higher.

Disk group attributes were introduced in ASM version 11.1[1] and can be used to fine tune the disk group properties. It is worth noting that some attributes can be set only at the time the disk group is created, while other attributes can be set at any time. Some attributes might be stored in the disk header, for example the AU_SIZE, while some other attributes, for (more...)

ASM file number 8

Database Management and Performance
| Jan 8, 2012

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

Database Management and Performance
| Jan 7, 2012

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

Database Management and Performance
| Jan 6, 2012

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

(more...)

ASM file number 5

Database Management and Performance
| Jan 4, 2012

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...)