Oracle ASM Filter Driver (Oracle ASMFD) is a kernel module that resides in the I/O path of the Oracle ASM disks. Oracle ASM uses the filter driver to validate write I/O requests to Oracle ASM disks.

Oracle ASMFD simplifies the configuration and management of disk devices by eliminating the need to rebind disk devices used with Oracle ASM each time the system is restarted.

Oracle ASM Filter Driver rejects any I/O requests that are invalid. This action eliminates accidental overwrites of Oracle ASM disks that would cause corruption in the disks and files within the disk group. For example, the Oracle ASM Filter Driver filters out all non-Oracle I/Os which could cause accidental overwrites.

You can configure Oracle ASM Filter Driver (Oracle ASMFD) for device persistence during the installation of Oracle Grid Infrastructure or after Oracle Grid Infrastructure has been installed.

• Configuring Oracle ASM Filter Driver During Installation

• Configuring Oracle ASM Filter Driver After Installation

If ASMLIB is installed and configured for an existing Oracle ASM installation, then you must explicitly uninstall the existing ASMLIB configuration before installing and configuring Oracle ASMFD.

Oracle recommends that you temporarily move Oracle Cluster Registry (OCR) and voting files to another disk group if one is available, as described in Migrating Oracle ASM Disk Groups without Oracle Cluster Registry or Voting Files, and migrate the disk group to use Oracle ASMFD. After migrating the disk group to use Oracle ASMFD, move OCR and voting files back to the disk group. You can similarly migrate any other disk groups if they contain OCR or voting files to ensure online migration of all disk groups to Oracle ASMFD.

This section contains the following topics:

• Migrating Oracle ASM Disk Groups without Oracle Cluster Registry or Voting Files

• Migrating Oracle ASM Disk Groups with Oracle Cluster Registry or Voting Files

• Migrating Oracle ASM Disk Groups in an Oracle Grid Infrastructure Standalone Environment

The value of the AFD_STATE parameter of SYS_ASMFD_PROPERTIES specifies whether Oracle ASMFD is configured for the Oracle ASM instance.

You can check the state of Oracle ASMFD with the ASMCMD afd_state command. For example:

$ $ORACLE_HOME/bin/asmcmd afd_state
ASMCMD-9526: The AFD state is 'LOADED' and filtering is 'DEFAULT' on host 'myhost'

For information about using the ASMCMD afd_state command to determine the state of Oracle ASMFD, refer to "afd_state".

To determine if Oracles ASMFD is present on the host, you can also display the value of AFD_STATE from SYS_CONTEXT. You must run the query on the Oracle ASM instance.

If the value of AFD_STATE is equal to NOT AVAILABLE, then Oracle ASMFD is not configured.

SQL> SELECT SYS_CONTEXT('SYS_ASMFD_PROPERTIES', 'AFD_STATE') FROM DUAL;
SYS_CONTEXT('SYS_ASMFD_PROPERTIES','AFD_STATE')
--------------------------------------------------------------------------------
NOT AVAILABLE

A value of CONFIGURED means that Oracle ASMFD is completely set up and the Oracle ASM instance can register with the driver.

SQL> SELECT SYS_CONTEXT('SYS_ASMFD_PROPERTIES', 'AFD_STATE') FROM DUAL;
SYS_CONTEXT('SYS_ASMFD_PROPERTIES','AFD_STATE')
--------------------------------------------------------------------------------
CONFIGURED

The AFD_DISKSTRING parameter specifies the Oracle ASMFD disk discovery string that is used to identify the disks to be managed by Oracle ASMFD.

You can set and display the AFD_DISKSTRING parameter with the ASMCMD afd_dsset and afd_dgset commands. For example:

$ $ORACLE_HOME/bin/asmcmd afd_dsset '/dev/rdsk/mydisks/*'

$ $ORACLE_HOME/bin/asmcmd afd_dsget
AFD discovery string: /dev/rdsk/mydisks/*

For information about ASMCMD commands to display and set the Oracle ASMFD disk discovery string, refer to "afd_dsget" and "afd_dsset".

You can also set the AFD_DISKSTRING with the ALTER SYSTEM SQL statement. A label is created in the disk header of those disks identified by the Oracle ASMFD disk discovery string.

SQL> ALTER SYSTEM AFD_DISKSTRING SET '/dev/disk0','/dev/disk1','/devices/dsk/*';
System altered.

You can retrieve the value of AFD_DISKSTRING parameter with the following query.

SQL> SELECT SYS_CONTEXT('SYS_ASMFD_PROPERTIES', 'AFD_DISKSTRING') FROM DUAL;
SYS_CONTEXT('SYS_ASMFD_PROPERTIES','AFD_DISKSTRING')
--------------------------------------------------------------------------------
'/dev/disk0','/dev/disk1','/devices/dsk/*'

You can update the Oracle ASM disk discovery string to add or remove Oracle ASMFD disk label names to and from the ASM_DIKSTRING initialization parameter.

For example, you can add the Oracle ASMFD disks to the ASM_DIKSTRING initialization parameter as follows:

ASM_DISKSTRING = 'AFD:DISK0', 'AFD:DISK1', '/dev/rdsk/mydisks/*'

Or you can set the ASM_DIKSTRING initialization parameter as follows:

ASM_DISKSTRING = 'AFD:*', '/dev/rdsk/mydisks/*'

You can display and set the Oracle ASM disk discovery string with the ASMCMD dsget and dsset commands. For example, you can set the Oracle ASM disk discovery string to add Oracle ASMFD disks as follows:

$ $ORACLE_HOME/bin/asmcmd dsset 'AFD:*,/dev/rdsk/mydisks/*'

You can remove previously added Oracle ASMFD disks as follows:

$ $ORACLE_HOME/bin/asmcmd dsset '/dev/rdsk/mydisks/*'

For information about ASMCMD commands to display and set the Oracle ASM disk discovery string, refer to "dsget" and "dsset".

For information about the ASM_DISKSTRING initialization parameter, refer to "ASM_DISKSTRING".

Setting a label provisions a disk to be used by Oracle ASMFD. After the label is set, the specified disk is managed by Oracle ASMFD.

You can add, remove, and scan labels with the ASMCMD afd_label, afd_unlabel, and afd_scan commands. For example:

$ $ORACLE_HOME/bin/asmcmd afd_label 'disk0' '/dev/rdsk/mydisks/disk0'

$ $ORACLE_HOME/bin/asmcmd afd_unlabel 'disk0'

$ $ORACLE_HOME/bin/asmcmd afd_scan '/dev/rdsk/mydisks/*'

For information about ASMCMD commands to add and remove labels on Oracle ASMFD disks, refer to "afd_label", "afd_unlabel", and "afd_scan". In addition, ASMCA provides support for adding and removing labels on Oracle ASMFD disks. For information about using ASMCA to administer disk groups, refer to "Managing Disk Groups with ASMCA".

You can also manage labels with SQL statements. You can set a label with the ALTER SYSTEM LABEL SET SQL statement. For example:

SQL> ALTER SYSTEM LABEL SET 'disk0' TO '/dev/disk0';
System altered.

SQL> SELECT UPPER(path) FROM V$ASM_DISK ORDER BY PATH;
UPPER(PATH)
--------------------------------------------------------------------------------
AFD:DISK0

When you run the statement, you can use the optional RENAME or MIGRATE option. If a disk was previously provisioned for Oracle ASMFD, you can rename the label with the RENAME option. Note that the device should not be managed with Oracle ASMFD when the command is run. If a disk was previously used for an Oracle ASM disk group and the disk group has been dismounted, then you can label this disk using the MIGRATE option.

You can use ALTER SYSTEM LABEL CLEAR to remove the label from a device and stop Oracle ASMFD from managing the device. For example:

SQL> ALTER SYSTEM LABEL CLEAR 'disk0';
System altered.

You can use ALTER SYSTEM LABEL SCAN on remote nodes after the ALTER SYSTEM LABEL SET command is run on the local node.

Because ALTER SYSTEM LABEL SET statement writes the label on the disk header and the disk is shared across nodes, the same statement is not run on other nodes of the cluster.

If the device-path is not specified, then the statement uses the AFD_DISKSTRING parameter value to perform the scan operation.

SQL> ALTER SYSTEM LABEL SCAN

You can deconfigure Oracle ASM Filter Driver (Oracle ASMFD) if it has been configured on your system.

This section contains the following topics:

• "Deconfiguring Oracle ASM Filter Driver in an Oracle Grid Infrastructure Clusterware Environment"

• "Deconfiguring Oracle ASM Filter Driver in an Oracle Grid Infrastructure Standalone (Oracle Restart) Environment"

For information about the ASMCMD commands for administering Oracle ASMFD, refer to "ASMCMD Oracle ASM Filter Driver Management Commands".