| Element |
Description |
| Disk Group Name |
Name of the disk group. |
| Redundancy |
ASM requires at least two failure groups to create a normal redundancy disk groups and at least three failure groups to create a high redundancy disk group. This implies that if you do not explicitly define failure groups, a normal redundancy disk group requires at least two disks, and a high redundancy disk group requires at least 3 disks.
Choose one of the following redundancy types to set the redundancy for the disk group:
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High. The contents of the disk group are three-way mirrored by default. To create a disk group with high redundancy, you must specify at least 3 failure groups (a minimum of 3 devices). Although high-redundancy disk groups provide a high level of data protection, you must consider the higher cost of additional storage devices before deciding to use this redundancy level.
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Normal. By default ASM uses two-way mirroring for data files and three-way mirroring for control files, to increase performance and reliability. Alternatively, you can use two-way mirroring or no mirroring. A normal redundancy disk group requires a minimum of two failure groups (or two disk devices) if you use two-way mirroring. The effective disk space in a normal redundancy disk group is half the sum of the disk space in all of its devices. For most installations, Oracle recommends that you use normal redundancy disk groups.
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External. Files in an external redundancy disk group have no ASM mirroring. Requires a minimum of one disk device. The effective disk space in an external redundancy disk group is the sum of the disk space in all of its devices. If you select this option, ASM does not mirror the contents of the disk group.
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| Select Member Disks |
Click the Show Candidates option to view all the disks that have a header status of CANDIDATE. To view all the disks that are discovered, click Show All.
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Disk Path. Physical path of the disk in the host system.
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Header Status. ASM instance ensures that any disk being included in the newly created disk group is addressable and is not already a member of another disk group. Disks that already belong to a disk group have a header status of MEMBER. Disks that were discovered but that are not yet assigned to a disk group have a header status of CANDIDATE. Disks that were previously assigned to a disk group have a header status of FORMER.
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Disk Name. Name of the Disk
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Size (MB). Size of the disk in MB.
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Failure Group. Failure groups define ASM disks that share a common failure mechanism. Failure groups are used to determine which ASM disks to use for storing redundant copies of data. For example, if 2-way mirroring is specified for a file, ASM automatically stores redundant copies of file extents in separate failure groups. Failure groups apply only to normal and high redundancy disk groups. Failure groups are defined for a disk group when you create or alter the disk group.
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Force. If the disk header indicates that it is part of another disk group, you can force it to become a member of the disk group you are creating by specifying the FORCE option. This option is used only if the disk group to which the disk belongs to has failed, and cannot be used otherwise. For example, a disk with an ASM header might have failed temporarily, so that its header could not be cleared when it was dropped from its disk group. After the disk is repaired, it is no longer part of any disk group, but it still has an ASM header. To use this disk in a new disk group, use the Force option. The operation fails if the original disk group is mounted, or if the disk does not have a disk group header. If a disk of a dismounted but properly working disk group is added to the disk groups being created by force, the former disk group cannot be used further.
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Quorum. Quorum failure groups are used to store voting files in extended clusters and do not contain any user data.
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| Change Disk Discovery Path |
Click Change Disk Discovery Path to discover additional disks that can be used by this ASM instance.
Note: Changing the disk discovery path will affect all the disk groups.
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| Allocation Unit Size |
An allocation unit (AU) is a measure of the contiguous disk space allocated to ASM files. |
| Compatibility |
Compatibility decides whether a user can leverage features in a new version of the product. ASM Compatibility is the minimum software version required for an ASM instance to mount this disk group (version 10.1 and above). Database Compatibility is the minimum software version required for a database instance to use files in this disk group (version 10.1 and above). ADVM Compatibility is the minimum software version required for an ASM volume to use this disk group (version 11.2 and above).
The Database and ADVM compatibility have to be less than or equal to the ASM compatibility. ASM compatibility must be atleast 11.1 to set database compatibility and 11.2 to set ADVM compatibility.
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