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Oracle® Automatic Storage Management Administrator's Guide
12c Release 1 (12.1)

E41058-08
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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 12.1 can take advantage of Oracle ASM 12c Release 1 (12.1) features. See Table 4-3 for the features enabled for combinations of compatibility attribute settings.

The disk group compatibility feature also enables environments to interoperate when they use disk groups from both Oracle Database 10g and Oracle Database 11g instances. For example, disk group compatibility settings that are set to Oracle Database 10g Release 2 (10.2) enable an Oracle Database 10g Release 2 (10.2) client to access a disk group created with Oracle ASM 12c Release 1 (12.1).

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 12.1, and RDBMS compatibility is set to 11.2, then the Oracle ASM software version must be at least 12.1, and the Oracle Database client software version must be at least 11.2. 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. See Table 4-2 for examples of valid combinations of compatible attribute settings.

The compatibility attributes are not set to zero releases, such as 11.0 or 12.0 or any value with all zeroes following the first dot.

You can set and update disk group attributes with the ASMCMD setattr command. For information about the ASMCMD setattr command, see "setattr".

Notes:

  • 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. See "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. These attributes are described under the following topics:

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.

For Oracle ASM 12c, 12.1 is the default setting for the COMPATIBLE.ASM attribute when using ASMCA. The default setting is 10.1 when using the SQL CREATE DISKGROUP statement and the ASMCMD mkdg command.

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 parameters of the databases are set to either 11.2 or 12.1, then COMPATIBLE.RDBMS can be set to any value between 10.1 and 11.2 inclusively.

For Oracle ASM 12c, 10.1 is the default setting for the COMPATIBLE.RDBMS attribute when using the SQL CREATE DISKGROUP statement, the ASMCMD mkdg command, and ASMCA.

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. See Oracle Database Reference for more information about the COMPATIBLE initialization parameter.

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.

By default, the value of the COMPATIBLE.ADVM attribute is empty until set.

For more information about Oracle ADVM, see "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 Chapter 9, "Managing Oracle ASM With ASMCA" and Chapter 10, "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 '11.2' or '12.1'; Oracle assumes that any missing version number digits are zeros.

Table 4-2 shows some valid combinations of the disk group compatibility attributes and the valid Oracle ASM and database instance versions for each combination.

Table 4-2 Examples of disk group compatibility attribute settings

COMPATIBLE.ASM COMPATIBLE.RDBMS COMPATIBLE.ADVM Oracle ASM Instance Version COMPATIBLE Setting for RDBMS Instance

10.1

10.1

n/a

>= 10.1

>= 10.1

11.1

10.1

n/a

>= 11.1

>= 10.1

11.2

11.2

11.2

>= 11.2

>= 11.2

12.1

12.1

12.1

>= 12.1

>= 12.1


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 disk group features enabled for this combination of attribute settings are shown in Table 4-3.

  • The database release is Oracle Database 12c Release 1 (12.1) (database initialization parameter COMPATIBLE is set to 12.1) and the Oracle ASM release is Oracle ASM 12c Release 1 (12.1). All the disk group compatibility attributes are set to 12.1 for a disk group.

    The disk group features enabled for this combination of attribute settings are shown in Table 4-3.

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 12.1 and the RDBMS compatibility set to the default (the COMPATIBLE.RDBMS default is less than or equal to 12.1):

CREATE DISKGROUP data1 DISK '/dev/sd*' 
       ATTRIBUTE 'compatible.asm' = '12.1';

The following example creates a normal redundancy disk group data2 with the ASM, RDBMS, and ADVM compatibility set to 12.1:

CREATE DISKGROUP data2 DISK '/dev/sd*' 
       ATTRIBUTE 'compatible.asm' = '12.1', 'compatible.rdbms' = '12.1',
                 'compatible.advm' = '12.1';

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 4-2. 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 12.1. An Oracle ASM instance must be at Oracle ASM 12c Release 1 (12.1) or higher to access the data3 disk group.

ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.asm' = '12.1';

The following example advances the COMPATIBLE.RDBMS and COMPATIBLE.ADVM compatibility attributes of the disk group data3 to 12.1. This example assumes that the value of COMPATIBLE.ASM is set to 12.1.

ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.rdbms' = '12.1',
ALTER DISKGROUP data3 SET ATTRIBUTE 'compatible.advm' = '12.1';

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.

See Example 6-1, "Viewing disk group attributes with V$ASM_ATTRIBUTE" for an example querying the V$ASM_ATTRIBUTE view.

You can also display the disk group compatibility attributes with the ASMCMD command lsattr. For information about lsattr, see "lsattr".

See Also:

Reverting Disk Group Compatibility

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:

  1. 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;
      
  2. If the OCR and voting files are in the disk group, move them out of this disk group.

    See Also:

    The Oracle Clusterware Administration and Deployment Guide for information about administering OCR and voting files
  3. 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.

  4. Create a new disk group using SQL CREATE DISKGROUP specifying the previous values for the disk group attribute settings.

    For information about creating a disk group, see "Using the CREATE DISKGROUP SQL Statement".

  5. 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).

    For information about moving data files between disk groups, refer to "Moving Data Files Between Disk Groups With ALTER DATABASE".

    For information about moving database files with RMAN, refer to "Moving Data Files Between Oracle ASM Disk Groups Using RMAN".

    See Also:

    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.
  6. 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.

    For information about dropping a disk group, see "Dropping Disk Groups".

Features Enabled By Disk Group Compatibility Attribute Settings

Table 4-3 describes the Oracle ASM features enabled by valid combinations of the disk group compatibility attribute settings.

Table 4-3 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

Intelligent Data Placement

>= 11.2

>= 11.2

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

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


Table 4-4 describe the Oracle ACFS features enabled by valid combinations of the disk group compatibility attribute settings.

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

Disk Group Features Enabled COMPATIBLE.ASM COMPATIBLE.RDBMS COMPATIBLE.ADVM

Volumes in disk groups

>= 11.2

n/a

>= 11.2

Encryption, replication, security, tagging (Linux systems)

>= 11.2.0.2

n/a

>= 11.2.0.2

Read-only snapshots

>= 11.2.0.2

n/a

>= 11.2.0.2

Encryption, replication, security, tagging (Windows systems)

>= 11.2.0.3

n/a

>= 11.2.0.3

Read-write snapshots

>= 11.2.0.3

n/a

>= 11.2.0.3

Unlimited file system expansion

>= 11.2.0.4

n/a

>= 11.2.0.4

Performance and scalability improvements in ls and find

>= 11.2.0.4

n/a

>= 11.2.0.4

Storing database data files and redo logs in Oracle ACFS file systems (on Windows the software must be 12.1.0.2 or higher and COMPATIBLE.ADVM must be set to 12.1.0.2)

>= 12.1

n/a

>= 12.1

Encryption, replication, security, tagging (Solaris systems)

>= 12.1

n/a

>= 12.1

Replication and tagging (AIX systems)

>= 12.1

n/a

>= 12.1

Creation from an existing snapshot and conversion of a snapshot

>= 12.1

n/a

>= 12.1

Support for 1023 snapshots

>= 12.1

n/a

>= 12.1.0.2

Accelerator volume for Oracle ACFS file system

>= 12.1

n/a

>= 12.1.0.2


The following list applies to Table 4-3 and Table 4-4.

  • 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.

  • All database files for Oracle Database can be stored in Oracle ACFS starting with Oracle Database 11g Release 2 (11.2.0.4), except for data files and redo logs in an Oracle Restart configuration. Using replication or encryption with database files on Oracle ACFS is not supported. For additional information, including any limitations or restrictions about storing data files in an Oracle ACFS file system, refer to "Overview of Oracle ACFS".

  • Oracle ASM and Oracle ACFS features not explicitly listed in Table 4-3 and Table 4-4 do not require advancing the disk group compatibility attribute settings.

  • Oracle ASM and Oracle ACFS features explicitly identified by an operating system in Table 4-3 and Table 4-4 are available on that operating system starting with the associated disk group attribute settings.

  • The value of COMPATIBLE.ASM must always be greater than or equal to the value of COMPATIBLE.RDBMS and COMPATIBLE.ADVM.

  • A value of not applicable (n/a) means that the setting of the attribute has no effect on the feature.

  • For information about the rebalancing process and the ASM_POWER_LIMIT initialization parameter, refer to "ASM_POWER_LIMIT".

Considerations When Setting Disk Group Compatibility in Replicated Environments

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. 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 COMPATIBLE.RDBMS settings when the AU_SIZE attribute is set to one megabyte for a disk group.

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

Redundancy COMPATIBLE.RDBMS = 10.1 COMPATIBLE.RDBMS >= 11.1

External

16 TB

140 PB

Normal

5.8 TB

23 PB

High

3.9 TB

15 PB


Table 4-5 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.

For information about Oracle ASM storage sizes, see "Oracle ASM Storage Limits".

See Also: