Managing Disk Group Attributes

Disk group attributes are parameters that are bound to a disk group, rather than an Oracle ASM instance. Some disk group attributes can be set when a disk group is created or altered. Other disk attributes can only be set when a disk group is created or only be set when a disk group is altered.

This section contains the following topics:

In addition to the disk group attributes listed in this section, template attributes are also assigned to a disk group. For information about template attributes, see Managing Disk Group Templates.

About Viewing and Setting Disk Group Attributes

You can set and display disk group attribute settings.

You can display disk group attributes with the V$ASM_ATTRIBUTE view and the ASMCMD lsattr command.

Disk group attributes can be set with the ATTRIBUTE clause of the ALTER DISKGROUP or CREATE DISKGROUP SQL statement and the ASMCMD setattr and mkdg commands.

See Also:

Example 6-1 for an example of the use of the V$ASM_ATTRIBUTE view
lsattr for information about the lsattr command
setattr for information about the setattr command
mkdg for information about the mkdg command
Managing Disk Groups with ASMCA for information about setting disk group attributes with Oracle ASM Configuration Assistant (ASMCA)

Summary of Disk Group Attributes

The Oracle ASM disk group attributes are listed in this section.

ACCESS_CONTROL.ENABLED

This attribute configures Oracle ASM File Access Control and can only be set when altering a disk group.

For information about the ACCESS_CONTROL.ENABLED attribute, see Setting Disk Group Attributes for Oracle ASM File Access Control.

ACCESS_CONTROL.UMASK

This attribute configures Oracle ASM File Access Control and can only be set when altering a disk group.

For information about the ACCESS_CONTROL.UMASK attribute, see Setting Disk Group Attributes for Oracle ASM File Access Control.

AU_SIZE

This attribute specifies allocation unit (AU) size and can only be set when creating a disk group. Example 4-1 shows how the AU_SIZE is specified with the CREATE DISKGROUP SQL statement.

For information about allocation units, refer to About Oracle ASM Allocation Units.

CELL.SMART_SCAN_CAPABLE

This attribute is only applicable to the configuration of Oracle Exadata storage.

See Also:

Oracle Exadata documentation

CELL.SPARSE_DG

This attribute is only applicable to the configuration of Oracle Exadata storage.

See Also:

Oracle Exadata documentation

COMPATIBLE.ASM

This attribute specifies the Oracle ASM compatibility level of a disk group. Compatibility attributes can be set when the disk group is created and advanced when a disk group is altered, but compatibility attributes cannot be reversed. For information about the COMPATIBLE.ASM attribute, refer to Disk Group Compatibility Attributes.

COMPATIBLE.RDBMS

This attribute specifies the database compatibility level of a disk group. Compatibility attributes can be set when the disk group is created and advanced when a disk group is altered, but compatibility attributes cannot be reversed. For information about the COMPATIBLE.RDBMS attribute, refer to Disk Group Compatibility Attributes.

COMPATIBLE.ADVM

This attribute specifies the Oracle Automatic Storage Management Cluster File System (Oracle ACFS) and Oracle ASM Dynamic Volume Manager (Oracle ADVM) compatibility level of a disk group. Compatibility attributes can be set when the disk group is created and advanced when a disk group is altered, but compatibility attributes cannot be reversed. For information about the COMPATIBLE.ADVM attribute, refer to Disk Group Compatibility Attributes and Overview of Oracle ASM Dynamic Volume Manager.

CONTENT.CHECK

The CONTENT.CHECK attribute enables or disables content checking when performing data relocation operations for a disk group.

The attribute value can be set to true (enabled) or false (disabled).

When CONTENT.CHECK is enabled, an Oracle ASM relocation process (rebalance, resync, or resilver) detects corruptions during a data copy operation and performs automatic block corruption recovery by replacing these corruptions with an uncorrupted mirror copy if one is available.

The content check process detects and repairs corruptions for situations when the I/O operation is successful, but the blocks have invalid content. The process also performs a Hardware Assisted Resilient Data (HARD) check for all supported files and a block header check for data files.

This attribute can only be set when altering a disk group.

See Also:

Manually Rebalancing Disk Groups and Tuning Rebalance Operations for information about disk group rebalancing

CONTENT.TYPE

This attribute identifies the disk group type: data, recovery, or system. The type value determines where Oracle ASM places the nearest neighbor disk in the failure group where Oracle ASM mirrors copies of the data. Oracle ASM uses this attribute value to make it less likely that a double failure in the storage medium causes disk groups of different content types to become unavailable. Specifying this attribute enables Oracle ASM to better deploy all disk groups in the available storage.

The default value is data which specifies a distance of 1 to the nearest neighbor disk. A value of recovery specifies a distance of 3 to the nearest neighbor disk and a value of system specifies a distance of 5.

The attribute can be specified when creating or altering a disk group. If CONTENT.TYPE attribute is set or changed using ALTER DISKGROUP, then the new configuration does not take effect until a disk group rebalance is explicitly run.

The CONTENT.TYPE attribute is only valid for disk groups that are set to normal or high redundancy. The COMPATIBLE.ASM attribute must be set to 11.2.0.3 or higher to enable the CONTENT.TYPE attribute for the disk group.

This attribute can be set with ASMCMD mkdg or SQL CREATE and ALTER DISKGROUP statements.

For example:

SQL> CREATE DISKGROUP data NORMAL REDUNDANCY
        FAILGROUP controller1 DISK
        '/devices/diska1' NAME diska1,
...
        ATTRIBUTE 
        'compatible.asm' = '12.1.0.1', 
        'content.type' = 'recovery',
...

SQL> ALTER DISKGROUP data SET ATTRIBUTE 'content.type' = 'data';

This attribute is primarily intended for use with Oracle Exadata storage.

For information about disk resync, see Oracle ASM Fast Mirror Resync.

See Also:

Oracle Exadata documentation
My Oracle Support (https://support.oracle.com) for information about using the CONTENT.TYPE attribute with Oracle Exadata storage

CONTENT_HARDCHECK.ENABLED

The CONTENT_HARDCHECK.ENABLED disk group attribute enables or disables Hardware Assisted Resilient Data (HARD) checking when performing data copy operations for rebalancing a disk group.

The attribute value can be set to true or false. This attribute can only be set when altering a disk group.

When the CONTENT.CHECK disk group attribute is set to enabled (true), the setting of CONTENT_HARDCHECK.ENABLED is ignored and checking is done on the content of user data, including HARD checks.
When the CONTENT.CHECK attribute is set to disabled (false) and the CONTENT_HARDCHECK.ENABLED attribute is set to enabled (true), only HARD checking is performed.
When the CONTENT.CHECK attribute is set to disabled (false) and the CONTENT_HARDCHECK.ENABLED attribute is set to disabled (false), no checking is performed.

See Also:

Manually Rebalancing Disk Groups and Tuning Rebalance Operations for information about disk group rebalancing

DISK_REPAIR_TIME

This attribute specifies the time interval to repair a disk and bring it back online before initiating the drop operation. This attribute can only be set when altering a disk group and is only applicable to normal and high redundancy disk groups.

For information about disk repair time, see Oracle ASM Fast Mirror Resync.

FAILGROUP_REPAIR_TIME

This attribute specifies a default repair time for the failure groups in the disk group. The failure group repair time is used if Oracle ASM determines that an entire failure group has failed. The default value is 24 hours (24h). If there is a repair time specified for a disk, such as with the DROP AFTER clause of the SQL ALTER DISKGROUP OFFLINE DISK statement, that disk repair time overrides the failure group repair time.

This attribute can only be set when altering a disk group and is only applicable to normal and high redundancy disk groups.

For information about failure group repair time, see Oracle ASM Fast Mirror Resync.

IDP.BOUNDARY and IDP.TYPE

Note:

The Intelligent Data Placement (IDP) feature has been deprecated since Oracle ASM 12c Release 2 (12.2) and is planned for desupport in a future release.

These attributes are used to configure Oracle Exadata storage.

See Also:

Oracle Exadata documentation

LOGICAL_SECTOR_SIZE

The LOGICAL_SECTOR_SIZE disk group attribute specifies the logical sector size for a disk group. The value can be set when creating or altering a disk group.

The value of LOGICAL_SECTOR_SIZE specifies the smallest unit of I/O allowed on the disk group. The value must be less than or equal to the size of the SECTOR_SIZE disk group attribute.

COMPATIBLE.ASM must be set to 12.2 or greater to use the LOGICAL_SECTOR_SIZE disk group attribute.

For information about setting the LOGICAL_SECTOR_SIZE disk group attribute, see Specifying the Logical and Physical Sector Size.

For information about the SECTOR_SIZE disk group attribute, refer to SECTOR_SIZE.

PHYS_META_REPLICATED

This disk group attribute tracks the replication status of a disk group. When the Oracle ASM compatibility of a disk group is advanced to 12.1 or higher, the physical metadata of each disk is replicated. This metadata includes the disk header, free space table blocks, and allocation table blocks. The replication is performed online asynchronously. This attribute value is set to true by Oracle ASM if the physical metadata of every disk in the disk group has been replicated.

This disk group attribute is only defined in a disk group with the Oracle ASM disk group compatibility (COMPATIBLE.ASM) set to 12.1 and higher. This attribute is read-only and is intended for information only. A user cannot set or change its value. The values are either true or false.

PREFERRED_READ.ENABLED

In an Oracle extended cluster, which contains nodes that span multiple physically separated sites, the PREFERRED_READ.ENABLED disk group attribute controls whether preferred read functionality is enabled for a disk group.

If preferred read functionality is enabled, then this functionality enables an instance to determine and read from disks at the same site as itself, which can improve performance.

Each Oracle ASM instance in an Oracle extended cluster has the information to determine the site in which it is located. If preferred read functionality is enabled, then based on the site information, the preferred status for a disk is determined to be true if the disk is in the same site as the instance. Otherwise, if the disk is not located at the same site as the Oracle ASM instance, the preferred status for a disk is set to false.

For extended clusters, the preferred read setting is enabled by default with a TRUE setting for the PREFERRED_READ.ENABLED disk group attribute of each disk group. For clusters that are not extended (only one physical site), preferred read is disabled. Preferred read status applies to extended, normal, high, and flex redundancy disk groups.

Oracle Database 12c Release 2 (12.2) is required and COMPATIBLE.ASM must be set to 12.2 or greater to use PREFERRED_READ.ENABLED.

Whether or not PREFERRED_READ.ENABLED has been enabled, preferred read can be set at the failure group level on an Oracle ASM instance or a client instance in a cluster with the ASM_PREFERRED_READ_FAILURE_GROUPS initialization parameter, which is available for backward compatibility.

To determine whether a disk has preferred read status, you can check the PREFERRED_READ column of the V$ASM_DISK view.

See Also:

ASM_PREFERRED_READ_FAILURE_GROUPS for information about the ASM_PREFERRED_READ_FAILURE_GROUPS initialization parameter
About Oracle ASM Extended Disk Groups for information about Oracle ASM extended disk groups
Oracle Grid Infrastructure Installation and Upgrade Guide for information about Oracle extended clusters
Oracle Database Reference for information about all of the V$ASM* dynamic performance views

SCRUB_ASYNC_LIMIT

The SCRUB_ASYNC_LIMIT disk group attribute sets the maximum allowed outstanding parallel read requests for asynchronous scrubbing.

The range of values is 1 to 1024. The default value is 1.

COMPATIBLE.ASM must be set to 12.2 or greater to use this disk group attribute.

For information about the scrubbing operation, refer to Scrubbing Disk Groups.

SECTOR_SIZE

The SECTOR_SIZE disk group attribute specifies the sector size for a disk group. The value can be set when creating or altering a disk group.

The value of SECTOR_SIZE is used for the block size of newly-created redo logs and Oracle ACFS file systems. The value can be changed to facilitate migration of disks to different sector sizes. The value must be greater than or equal to the size of the LOGICAL_SECTOR_SIZE disk group attribute.

COMPATIBLE.ASM must be set to 12.2 or greater to use the 12.2 functionality of SECTOR_SIZE, which includes the ability to alter the sector size after a disk group has been created.

For information about setting the SECTOR_SIZE disk group attribute, see Specifying the Logical and Physical Sector Size.

For information about the LOGICAL_SECTOR_SIZE disk group attribute, refer to LOGICAL_SECTOR_SIZE.

STORAGE.TYPE

This disk group attribute specifies the type of the disks in the disk group. The possible values are AXIOM, ZFSSA, and OTHER. If the attribute is set to AXIOM or ZFSSA, then all disks in the disk group must be of that type. If the attribute is set to OTHER, then any types of disks can be in the disk group.

If the STORAGE.TYPE disk group attribute is set to AXIOM or ZFSSA, then functionality for Hybrid Columnar Compression (HCC) can be enabled for Pillar Axiom or ZFS storage.

Note:

Pillar Axiom storage must be added as SCSI/Fiber Channel.

To set the STORAGE.TYPE attribute, the COMPATIBLE.ASM and COMPATIBLE.RDBMS disk group attributes must be set to 11.2.0.3 or higher. For maximum support with ZFS storage, set the COMPATIBLE.ASM and COMPATIBLE.RDBMS disk group attributes to 11.2.0.4 or higher. For information about disk group compatibility attributes, refer to Disk Group Compatibility.

The STORAGE.TYPE attribute can be set when creating a disk group or when altering a disk group. The attribute cannot be set when clients are connected to the disk group. For example, the attribute cannot be set when an Oracle ADVM volume is enabled on the disk group.

The attribute is not visible in the V$ASM_ATTRIBUTE view or with the ASMCMD lsattr command until the attribute has been set.

See Also:

Oracle Database Concepts for more information about Hybrid Columnar Compression. Hybrid Columnar Compression is a feature of certain Oracle storage systems.

THIN_PROVISIONED

This attribute enables or disables the functionality to discard unused storage space after a disk group rebalance is completed. The attribute value can be true or false. The default value is false.

Storage vendor products that support thin provisioning have the capability to reuse the discarded storage space for a more efficient overall physical storage utilization.

Note:

The THIN_PROVISIONED attribute is supported only with Oracle ASM Filter Driver (Oracle ASMFD) in Oracle Grid Infrastructure 12.2 and later releases on Linux. For information about Oracle ASMFD, refer to Administering Oracle ASM Filter Driver. For additional information about Oracle ASMFD, such as supported operating system platforms (certification matrix) or configuration issues, refer to My Oracle Support articles available at My Oracle Support (https://support.oracle.com).

For information about disk group rebalancing, refer to Tuning Rebalance Operations.

VAM_MIGRATION_DONE

Virtual Allocation Metadata (VAM) supports flexible storage allocation. The VAM_MIGRATION_DONE disk group attribute must be enabled and the migration completed before migrating a NORMAL or HIGH redundancy disk group to a FLEX redundancy disk group without the use of a restrictive mount.