D    Data Management Applications Programming Interface (DMAPI)

DMAPI is a Common Applications Environment (CAE) standard that allows data management applications to interface with the underlying operating system. An example of a data management application is a hierarchical storage manager (HSM), which can use DMAPI features to migrate data to and from tertiary storage as well as to track file information.

DMAPI functionality requires an AdvFS Utilities license. See dmapi(3) to identify the data management operations that are supported.

Use the showfsets command to determine if a file is enabled for DMAPI. To enable a fileset for DMAPI, execute the chfsets command. You must have root user privilege.

A number of restrictions apply to DMAPI-enabled filesets:

• The DMAPI-enabled fileset must be the only fileset in its domain. You cannot clone or add a fileset to a domain that contains a DMAPI-enabled fileset.

• Filesets that are named root, usr, and var cannot be enabled for DMAPI. Also, DMAPI filesets should not be mounted on /, /usr, and /var.

• Only DVN4 domains are supported under DMAPI.

• Only one application should manage the DMAPI-enabled fileset. Allowing more than one application to operate on a fileset is not supported.

• Filesets must be unmounted before you can turn on DMAPI functionality.

• Do not mount a DMAPI-enabled fileset on a version of Tru64 UNIX that does not support DMAPI. This could result in file corruption.

• Tru64 UNIX does not support importing a fileset from another system if either an existing or the imported fileset is enabled for DMAPI.

• You cannot dump a DMAPI-enabled fileset by using the vdump command. Use the vendor-approved backup for your data management application.

• Quotas are not supported on DMAPI-enabled filesets.

• Do not use the salvage command to restore lost data on a DMAPI-enabled fileset. The salvage utility operates only on primary storage. This means that if the command is used on a DMAPI-enabled fileset, some files might be missing data that was made nonresident by the DMAPI application. Follow the procedures provided by the DMAPI application vendor.

• Utilities that manage storage, such as defragment, balance, migrate, and /sbin/advfs/verify, work on DMAPI-enabled filesets. However, running these utilities might result in less effective storage management than would occur without DMAPI being enabled.

• In the current DMAPI implementation, asynchronous event posting is reliable in all but the most unusual cases. For more information, see the CAE DMAPI standard under Event Types.

• Memory mapping is not supported on DMAPI-enabled filesets.

• The vfilepg command exits if a page is sparse. Because a page migrated out to tertiary storage by DMAPI appears as sparse in primary storage, the vfilepg command may not operate properly on DMAPI-enabled filesets.

To create a new domain and fileset and enable DMAPI for the fileset:

1. Create a new domain and fileset.

2. Turn on DMAPI functionality by using the chfsets command with the -o dmapi option.

3. Check the fileset status by using the showfsets command.

For example, to create the fileset sales_fset in the domain receipt_dmn:

# mkfdmn /dev/disk/dsk1c receipt_dmn
# mkfset receipt_dmn sales_fset
# chfsets -o dmapi receipt_dmn sales_fset 
# showfsets receipt_dmn

To enable an existing fileset for DMAPI:

1. Be certain only one fileset exists in the domain. If it does not:

   1. Dump the fileset by using the vdump command.

   2. Create a new domain and a new fileset. Because it is in a new domain, the fileset can have the same name as the old fileset.

   3. Restore the fileset to the new domain by using the vrestore command.

2. Unmount the fileset if needed.

3. Enable DMAPI by using the chfsets command.

4. Check the fileset status by using the showfsets command.

To disable DMAPI for a fileset:

1. Unmount the filesets.

2. Call the chfsets command with the -o nodmapi option.

3. Check the fileset status by using the showfsets command.

   Note that you can disable DMAPI only if the data management application has not begun modifying the fileset. In order to avoid the possibility of corruption, if it has begun you cannot disable DMAPI.

To check if DMAPI-managed regions are enabled on a file, execute the showfile command.

# showfile /mnt/file1
     Id Vol PgSZ Pages XtntType Segs SegSZ    I/O Perf File
 6.8006   1   16     4   simple   **    **  async 100% file1
  DMAPI regions present on this file.