Disk Group Compatibility

This section describes disk group compatibility under the following topics:

Overview of Disk Group Compatibility

Advancing the disk group compatibility settings enables you to use the new Oracle ASM features that are available in a later release. For example, a disk group with the disk group compatibility attributes set to 19.0 can take advantage of Oracle ASM 19c features. For information about the features enabled for combinations of compatibility attribute settings, refer to Table 4-4.

The disk group attributes that determine compatibility are COMPATIBLE.ASM, COMPATIBLE.RDBMS. and COMPATIBLE.ADVM. The COMPATIBLE.ASM and COMPATIBLE.RDBMS attribute settings determine the minimum Oracle Database software version numbers that a system can use for Oracle ASM and the database instance types respectively. For example, if the Oracle ASM compatibility setting is 19.0, and RDBMS compatibility is set to 12.2.0.1, then the Oracle ASM software version must be at least 19.0, and the Oracle Database client software version must be at least 12.2.0.1. The COMPATIBLE.ADVM attribute determines whether the Oracle ASM Dynamic Volume Manager feature can create a volume in a disk group.

When you create a disk group, you can specify the disk group compatibility attribute settings in the CREATE DISKGROUP SQL statement. The ALTER DISKGROUP SQL statement can update the compatible attribute settings for existing disk groups. For examples of valid combinations of compatible attribute settings, refer to Table 4-3.

You can also set and update disk group attributes with the ASMCMD setattr command. For information about the ASMCMD setattr command, refer to setattr.

Note:

The disk group compatibility settings determine whether your environment can use the latest Oracle ASM features.
The disk group compatibility settings can only be advanced; you cannot revert to a lower compatibility setting. For more information, refer to Reverting Disk Group Compatibility.
The COMPATIBLE.ASM attribute must be advanced before advancing other disk group compatibility attributes and its value must be greater than or equal to the value of other disk group compatibility attributes.

Disk Group Compatibility Attributes

The disk group compatibility attributes specify the disk group compatibility settings for Oracle ASM and database instances.

COMPATIBLE.ASM
COMPATIBLE.RDBMS
COMPATIBLE.ADVM

Note:

Starting with Oracle ASM version 12.2.0.1, the minimum and default settings for Oracle ASM disk group attributes are:

COMPATIBLE.ASM = 11.2.0.2 and COMPATIBLE.RDBMS = 10.1 for EXTERNAL, NORMAL, and HIGH redundancy disk groups
COMPATIBLE.ASM = 12.2.0.1 and COMPATIBLE.RDBMS = 12.2.0.1 for FLEX and EXTENDED disk groups

The default and minimum values for Oracle ASM disk group attributes are present when using SQL*Plus to create a disk group. Other utilities, such as ASMCA, may use a different default value when creating a disk group; however, the minimum value for Oracle ASM disk group attributes should be the same.

COMPATIBLE.ASM

The value for the disk group COMPATIBLE.ASM attribute determines the minimum software version for an Oracle ASM instance that can use the disk group. This setting also affects the format of the data structures for the Oracle ASM metadata on the disk. The format of other file contents is determined by Oracle ASM Dynamic Volume Manager (Oracle ADVM) and the database instance.

COMPATIBLE.RDBMS

The value for the disk group COMPATIBLE.RDBMS attribute determines the minimum COMPATIBLE database initialization parameter setting for any database instance that is allowed to use the disk group. Before advancing the COMPATIBLE.RDBMS attribute, ensure that the values for the COMPATIBLE initialization parameter for all of the databases that access the disk group are set to at least the value of the new setting for COMPATIBLE.RDBMS.

For example, if the COMPATIBLE initialization parameter of the databases is set to either 12.2, then COMPATIBLE.RDBMS can be set to any value between 10.1 and 12.2 inclusively. If the COMPATIBLE initialization parameter of the databases is set to 19.0, then COMPATIBLE.RDBMS can be set to any value between 10.1 and 19.0 inclusively.

Note:

The database initialization parameter COMPATIBLE enables you to use a new release of Oracle Database, while at the same time guaranteeing backward compatibility with an earlier release. For more information about the COMPATIBLE initialization parameter, refer to Oracle Database Reference.

COMPATIBLE.ADVM

The value for the disk group COMPATIBLE.ADVM attribute determines whether the disk group can contain Oracle ADVM volumes. The value must be set to 11.2 or higher. Before setting this attribute, the COMPATIBLE.ASM value must be 11.2 or higher. Also, the Oracle ADVM volume drivers must be loaded in the supported environment.

The default value of the COMPATIBLE.ADVM attribute depends on the level of the Oracle ASM release.

For more information about Oracle ADVM, refer to Overview of Oracle ASM Dynamic Volume Manager.

Setting Disk Group Compatibility Attributes

This section discusses the settings of the disk group compatibility attributes and how to set the attribute values with the CREATE DISKGROUP or ALTER DISKGROUP SQL statement.

This section contains these topics:

You can also set the disk group compatibility settings withOracle ASM command-line utility (ASMCMD) and Oracle ASM Configuration Assistant (ASMCA). Refer to Managing Oracle ASM With ASMCA and Managing Oracle ASM with ASMCMD .

Note:

Advancing the values for disk group compatibility attributes is an irreversible operation. See Reverting Disk Group Compatibility.

See Also:

Oracle Database SQL Language Reference for more information about the disk group compatibility SQL statements

Valid Combinations of Compatibility Attribute Settings

When setting the values for the disk group attributes, specify at least the major and minor versions of a valid Oracle Database release number. For example, you can specify compatibility as 12.2 or 19.0; Oracle assumes that any missing version number digits are zeros.

Oracle ASM features enabled for combinations of attribute settings are shown in Features Enabled By Disk Group Compatibility Attribute Settings.

Table 4-3 shows some valid combinations of the disk group compatibility attributes and the valid Oracle ASM and database instance versions for each combination.

Table 4-3 Examples of disk group compatibility attribute settings

COMPATIBLE.ASM	COMPATIBLE.RDBMS	COMPATIBLE.ADVM	Oracle ASM Instance Version	COMPATIBLE Setting for RDBMS Instance
12.1	12.1	12.1	>= 12.1	>= 12.1
12.2	12.1	12.2	>= 12.2	>= 12.1
18.0	18.0	18.0	>= 18.0	>= 18.0
19.0	19.0	19.0	>=19.0	>=19.0

These are some possible combinations of Oracle ASM and database releases:

The database release is Oracle Database 11g Release 2 (11.2) (database initialization parameter COMPATIBLE is set to 11.2) and the Oracle ASM release is Oracle ASM 11g Release 2 (11.2). The COMPATIBLE.ASM and COMPATIBLE.RDBMS disk group attributes are set to 10.2 for a disk group.

The Oracle ASM disk group functionality remains at Oracle Database 10g Release 2 (10.2).
The database release is Oracle Database 10g Release 1 (10.1) and the Oracle ASM release is 11.2. COMPATIBLE.ASM is set to 11.2 and COMPATIBLE.RDBMS is set to 10.1 for a disk group.
The database release is Oracle Database 12c Release 2 (12.2) (database initialization parameter COMPATIBLE is set to 12.2) and the Oracle ASM release is Oracle ASM 12c Release 2 (12.2). All the disk group compatibility attributes are set to 12.2 for a disk group.

Oracle ASM in a Domain Services Cluster and Oracle Database in a Member Cluster Configuration

Oracle ASM or Oracle IOServer running in a Domain Services Cluster (DSC) version 19.1 support Oracle Database and Oracle Grid Infrastructure running in Member Cluster versions 12.2 and 19.1.

Oracle ASM or Oracle IOServer running in a Domain Services Cluster (DSC) version 12.2 support Oracle Database and Oracle Grid Infrastructure running in Member Cluster versions 12.2 and 19.1.

An Oracle Database instance must be a version lower than or equal to the Oracle ASM version in the same cluster. However, this requirement is not strictly enforced when the database instance is connecting from a different cluster.

Using CREATE DISKGROUP with Compatibility Attributes

You can specify the compatibility settings for a disk group with the CREATE DISKGROUP statement when creating the disk group.

The following example creates a normal redundancy disk group data1 with the Oracle ASM compatibility set to 19.0 and the RDBMS compatibility set to the default (the COMPATIBLE.RDBMS default is less than or equal to 19.0):

CREATE DISKGROUP data1 DISK '/dev/sd*' 
       ATTRIBUTE 'compatible.asm' = '19.0';

The following example creates a normal redundancy disk group data2 with the ASM, RDBMS, and ADVM compatibility set to 19.0:

CREATE DISKGROUP data2 DISK '/dev/sd*' 
       ATTRIBUTE 'compatible.asm' = '19.0', 'compatible.rdbms' = '19.0',
                 'compatible.advm' = '19.0';

Using ALTER DISKGROUP with Compatibility Attributes

After a disk group has been created, you can use the ALTER DISKGROUP SQL statement to change the compatibility attributes. The ALTER DISKGROUP SQL statement ensures that Oracle can advance the compatibility of the specified disk group before committing the change.

All of the affected databases and file systems should be online when running ALTER DISKGROUP to ensure that advancing compatibility does not reduce the database and file system access. When advancing disk group compatibility, you must advance the COMPATIBLE.ASM attribute before the COMPATIBLE.RDBMS or COMPATIBLE.ADVM attribute to ensure a valid combination of compatible attribute settings as shown in Table 4-3. You can advance only one compatibility attribute in a single ALTER DISKGROUP statement.

The following example advances the Oracle ASM compatibility for disk group data3 to 19.0. An Oracle ASM instance must be at Oracle ASM 19c or higher to access the data3 disk group.

ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.asm' = '19.0';

The following example advances the COMPATIBLE.RDBMS and COMPATIBLE.ADVM compatibility attributes of the disk group data3 to 10.0. This example assumes that the value of COMPATIBLE.ASM is set to 19.0.

ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.rdbms' = '19.0',
ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.advm' = '19.0';

Viewing Compatibility Attribute Settings

You can view the disk group compatibility settings in the V$ASM_ATTRIBUTE view. However, the V$ASM_ATTRIBUTE view does not display any rows when the COMPATIBLE.ASM value is set to 10.1. Instead you can determine the values for the COMPATIBLE.ASM and COMPATIBLE.RDBMS disk group compatibility attributes with the COMPATIBILITY and DATABASE_COMPATIBILITY columns of the V$ASM_DISKGROUP view.

You can also display the disk group compatibility attributes with the ASMCMD command lsattr.

See Also:

Example 6-1 for an example querying the V$ASM_ATTRIBUTE view
lsattr for information about the ASMCMD lsattr command
Oracle Database SQL Language Reference for information about disk group attributes
Oracle Database Reference for details on the V$ASM_DISKGROUP and V$ASM_ATTRIBUTE dynamic performance views

Reverting Disk Group Compatibility

You cannot revert disk group compatibility to a previous values. Instead you must create a new disk group.

Advancing the values for disk group compatibility attributes is an irreversible operation. If you advance the disk group compatibility settings, you cannot change the values back to the previous settings. To revert to the previous values, you must create a new disk group with the old compatibility attribute settings and then restore the database files that were in the disk group to the new disk group.

When you revert to a new disk group with the old compatibility attribute settings, the latest Oracle ASM features might not be available. For example, if you revert the disk group compatibility to a pre-11.2 value, Oracle ACFS functionality is not available.

For example, you could perform the following procedure to revert a disk group to previous compatibility settings:

If the Oracle ASM SPFILE is in the disk group, move this SPFILE out of the disk group:
1. Connect with SQL*Plus to the Oracle ASM instance.
2. Create a PFILE in the file system.
  
  For example:
```
SQL> CREATE PFILE '$ORACLE_HOME/dbs/asmspfile.ora' FROM SPFILE;
```
If the OCR and voting files are in the disk group, move them out of this disk group.
Back up any files that must be saved.
1. Back up the database files.
2. If an Oracle ACFS file system is mounted on an Oracle ADVM volume on the disk group, the operating system files in the file system must be backed up or copied to a location outside the file system mount point.
Create a new disk group using SQL CREATE DISKGROUP specifying the previous values for the disk group attribute settings.
Move or restore the database files into the newly created disk group using either the ALTER DATABASE MOVE DATAFILE SQL statement or Recovery Manager (RMAN).
Drop the disk group with the advanced disk group compatibility settings using SQL DROP DISKGROUP INCLUDING CONTENTS to remove the disk group and its contents. This SQL statement also removes any Oracle ACFS file system and its contents.

See Also:

About Creating a Disk Group for information about creating a disk group
Moving Data Files Between Disk Groups With ALTER DATABASE for information about moving data files between disk groups
Moving Data Files Between Oracle ASM Disk Groups Using RMAN for information about moving database files with RMAN
Dropping Disk Groups for information about dropping a disk group
Oracle Clusterware Administration and Deployment Guide for information about administering OCR and voting files
Oracle Database Administrator’s Guide for information about using the ALTER DATABASE MOVE DATAFILE SQL statement to move data files between Oracle ASM disk groups

Features Enabled By Disk Group Compatibility Attribute Settings

Thi topic describes the Oracle ASM features enabled by valid combinations of the disk group compatibility attribute settings.

The following list applies to Oracle ASM features enabled by valid combinations of the disk group compatibility attribute settings.

The value of COMPATIBLE.ASM must always be greater than or equal to the value of COMPATIBLE.RDBMS and COMPATIBLE.ADVM.
Starting with Oracle Grid Infrastructure 12.2.0.1 software, the minimum setting for COMPATIBLE.ASM is 11.2.0.2.
A value of not applicable (n/a) means that the setting of the attribute has no effect on the feature.
Oracle ASM features not explicitly listed in the following table do not require advancing the disk group compatibility attribute settings.
Oracle ASM features explicitly identified by an operating system in the following table are available on that operating system starting with the associated disk group attribute settings.
If encryption is configured for the first time on Oracle ASM 11g Release 2 (11.2.0.3) on Linux or if encryption parameters must be changed or a new volume encryption key must be created following a software upgrade to Oracle ASM 11g Release 2 (11.2.0.3) on Linux, then the disk group compatibility attributes for ASM and ADVM must be set to 11.2.0.3 or higher.
Using replication or encryption with database files on Oracle ACFS is not supported.
Oracle ACFS on Oracle Exadata storage is supported starting with Oracle Grid Infrastructure 12.1.0.2 on Linux.

Table 4-4 Oracle ASM features enabled by disk group compatibility attribute settings

Disk Group Features Enabled	COMPATIBLE.ASM	COMPATIBLE.RDBMS	COMPATIBLE.ADVM
Support for larger AU sizes (32 or 64 MB)	>= 11.1	>= 11.1	n/a
Attributes are displayed in the `V$ASM_ATTRIBUTE` view	>= 11.1	n/a	n/a
Fast mirror resync	>= 11.1	>= 11.1	n/a
Variable size extents	>= 11.1	>= 11.1	n/a
Exadata storage	>= 11.1.0.7	>= 11.1.0.7	n/a
OCR and voting files in a disk group	>= 11.2	n/a	n/a
Sector size set to nondefault value	>= 11.2	>= 11.2	n/a
Oracle ASM SPFILE in a disk group	>= 11.2	n/a	n/a
Oracle ASM File Access Control	>= 11.2	>= 11.2	n/a
`ASM_POWER_LIMIT` value up to `1024`	>= 11.2.0.2	n/a	n/a
Content type of a disk group	>= 11.2.0.3	n/a	n/a
Appliance mode for Oracle Exadata (no fixed partnering)	>= 11.2.0.4	n/a	n/a
Replication status of a disk group	>= 12.1	n/a	n/a
Managing a shared password file in a disk group	>= 12.1	n/a	n/a
Greater than 2 TB Oracle ASM disks without Oracle Exadata storage	>= 12.1	>= 12.1	n/a
Fixed partnering for Oracle Exadata	>= 12.1.0.2	n/a	n/a
Appliance mode for Oracle Data Appliance (ODA)	>= 12.1.0.2	n/a	n/a
Support for Oracle Exadata sparse disk groups	>= 12.1.0.2	>= 12.1.0.2	n/a
Support for resync checkpoint	>= 12.1.0.2	>= 12.1.0.2	n/a
`LOGICAL_SECTOR_SIZE`	>= 12.2	n/a	n/a
Altering sector size	>= 12.2	n/a	n/a
Oracle ASM flex and extended disk groups	>= 12.2	>= 12.2	n/a
`SCRUB_ASYNC_LIMIT`	>= 12.2	n/a	n/a
`PREFERRED_READ.ENABLED` Oracle Database 12c Release 2 (12.2) is required.	>=12.2	n/a	n/a
Converting normal or high redundancy disk groups to flex disk groups without restricted mount	>=18.0	>=12.2	n/a
Oracle ASM flex disk group support for multitenant cloning	>=18.0	>=18.0	n/a
Storage conversion for member clusters	>=18.0	n/a	n/a
Virtual Allocation Metadata (VAM) enabled on non-sparse normal and high redundancy disk groups	>=18.0	n/a	n/a

See Also:

Oracle ACFS Features Enabled by Compatibility Attribute Settings for information about Oracle ACFS features enabled by disk group compatibility settings
Overview of Oracle ACFS for information, including any limitations or restrictions, about storing data files in an Oracle ACFS file system
ASM_POWER_LIMIT for information about the rebalancing process and the ASM_POWER_LIMIT initialization parameter

Considerations When Setting Disk Group Compatibility

If you advance disk group compatibility, then you could enable the creation of files that are too large to be managed by a previous release of Oracle Database.

For example, you must be aware of the file size limits because replicated sites cannot continue using the software from a previous release to manage these large files. The disk group compatibility settings should be the same for all replicated environments.

Table 4-5 shows the maximum Oracle ASM file sizes supported for multiple COMPATIBLE.RDBMS settings with the AU_SIZE disk group attribute set to 1 MB. This table shows that Oracle Database 10g can only support a file size of up to 16 TB for external redundancy. If you advance the COMPATIBILE.RDBMS attribute to 11.1 or greater, then a file can grow beyond 16 TB. However, the larger size causes the file to be unusable in a replicated and disaster recovery site if the disaster recovery site has a disk group COMPATIBLE.RDBMS setting that is incompatible with the larger size.

Table 4-5 Maximum Oracle ASM file sizes for disk groups with AU_SIZE set to 1 MB

Redundancy	COMPATIBLE.RDBMS = 10.1	COMPATIBLE.RDBMS >= 11.1
External	16 TB	128 TB
Normal	5.8 TB	93 TB
High	3.9 TB	62 TB

Table 4-6 shows the maximum Oracle ASM file sizes supported for multiple COMPATIBLE.RDBMS settings with the AU_SIZE disk group attribute set to 4 MB.

Table 4-6 Maximum Oracle ASM file sizes for disk groups with AU_SIZE set to 4 MB

Redundancy	COMPATIBLE.RDBMS = 10.1	COMPATIBLE.RDBMS >= 11.1
External	64 TB	128 TB
Normal	32 TB	128 TB
High	21 TB	128 TB

Note:

The 128 TB limit under the COMPATIBLE.RDBMS >= 11.1 column in tables Table 4-5 and Table 4-6 is not a limit specific to Oracle ASM. The limit is specific to the database data file, which is calculated as 2^2 * logical block size. The block size can be at most 32 KB, or 2^5. The resulting calculation is 2^2 * 2^5 = 2^7, or 128 TB.

See Also:

Oracle ASM Storage Limits for information about Oracle ASM storage sizes
Oracle Database Upgrade Guide for information about database compatibility
Oracle Database Administrator’s Guide for information about the COMPATIBLE initialization parameter and irreversible compatibility
Oracle Database Reference for information about the COMPATIBLE initialization parameter