Glossary
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## Glossary

active database entry

  A valid daemon database entry. See also soft-deleted database entry and hard-deleted database entry.

alternate media

  The media onto which migrated data blocks are stored, usually tapes.

automated space management

  The combination of utilities that allows DMF to maintain a specified level of free space on a file system through automatic file migration.

base object

  The configuration object that defines path name and file size parameters necessary for DMF operation.

bitfile ID

  See bfid.

bfid

  The bit file identifier, or bfid, is a unique identifier, assigned to each file during the migration process, that links a migrated file to its data on alternate media.

bfid set

  The collection of database entries and the user file associated with a particular bfid.

bfid-set state

  The sum of the states of the components that comprise a bfid set: the file state of any user file and the state of any database entries (incomplete, complete, soft-deleted, or active).

block

  Physical unit of I/O to and from media, usually tape. The size of a block is determined by the type of device being written. A tape block is accompanied by a header identifying the chunk number, zone number, and its position within the chunk.

candidate list

  A list that contains an entry for each file in a file system eligible for migration, ordered from largest file weight (first to be migrated) to smallest. This list is generated and used internally by `dmfsmon(8)`. The `dmscanfs(8)` command prints similar file status information to standard output.

CAT records

  The catalog (CAT) records in the tape MSP database that track which migrated files reside on which tape volumes.

chunk

  That portion of a user file that fits on the current media (tape) volume. Most small files are written as single chunks. When a migrated file cannot fit onto a single volume, the file is split into chunks.

complete MSP daemon-database entry

  An entry in the daemon database whose `path` field contains a key returned by its MSP, indicating that the MSP maintains a valid copy of the user file.

compression

  The mechanism provided by the tape MSP for copying active data from volumes that contain largely obsolete data to volumes that contain mostly active data. This process is also known as volume merging or tape merging.

configuration object

  A series of parameter definitions in the DMF configuration file that controls the way DMF operates. By changing the parameters associated with objects, you can modify the behavior of DMF.

configuration parameter

  A string in the DMF configuration file that defines a part of a configuration object. By changing the values associated with these parameters, you can modify the behavior of DMF. The parameter serves as the name of the line. Some parameters are reserved words, some are supplied by the site.

daemon database

  A database maintained by the DMF daemon. This database contains such information as the bfid, the MSP name, and MSP key for each copy of a migrated file.

daemon object

  The configuration object that defines parameters necessary for `dmdaemon(8)` operation

data-pointer area

  The portion of the inode that points to the file's data blocks.

device object

  The configuration objects that define parameters for DMF's use of tape devices.

direct-access storage device (DASD)

  An IBM disk drive.

DMF state

  See file state.

dual-state file

  A file whose data resides both online and offline.

dual-state file systems

  Those file systems that have the necessary inode space to support dual-state files.

fhandle

  See file handle.

file

  An inode and its associated data blocks; an empty file has an inode but no data blocks.

file handle

  The DMAPI identification for a file. You can use the `dmscanfs(8)`, `dmattr(1)`, and `dmfind(1)` commands to find file handles.

file state

  The migration state of a file as indicated by the `dmattr(1)` command. A file can be regular (not migrated), migrating, dual-state, offline, unmigrating, never-migrated, or have an invalid DMF state.

freed file

  A user file that has been migrated and whose data blocks have been released.

fully backed up file

  A file that has one or more complete offline copies and no pending or incomplete offline copies.

hard-deleted database entry

  An MSP database entry that has been removed from the daemon database and whose MSP copy has been discarded. See also active database entry and soft-deleted database entry.

inode

  The portion of a file that contains the bfid, the state field, and the data pointers.

incomplete MSP daemon-database entry

  An entry in the daemon database for an MSP that has not finished copying the data, and therefore has not yet returned a key. The `path` field in the database entry is NULL.

incompletely migrated file

  A file that has begun the migration process, but for which one or more copies on alternate media have not yet been made.

media-specific process (MSP)

  The daemon-like process by which data blocks are copied onto alternate media, and which assigns keys to identify the location of the migrated data.

migrated file

  A file that has a bfid and whose offline copies (or copy) are completed. Migrated files can be dual-state or offline.

migrating file

  A file that has a bfid but whose offline copies (or copy) are in progress.

MSP

  See media-specific process (MSP).

MSP database entry

  The configuration objects that define parameters necessary for that MSP's operation. There is one MSP object for each MSP.

MSP objects

  The configuration objects that define parameters necessary for that MSP's operation

nonmigrated file

  A file that does not have a bfid or any offline copies. See regular file.

offline file

  A file whose inode contains a bfid but whose disk blocks have been removed. The file's data exists elsewhere in copies on alternate media.

offline pointer

  In tape MSP processing, a character string that the MSP returns to the daemon to indicate how a file is to be retrieved. For the tape MSP, the offline pointer is the character key into the MSP catalog (CAT) records of the database.

orphan chunks

  Unused chunks in the tape MSP catalog (CAT) database entries resulting from the removal of migrated files.

orphan database entries

  Unused database entries resulting from the removal of migrated files during a period in which the DMF daemon is not running.

parameter

  See configuration parameter.

policy objects

  The configuration objects that specify parameters to determine MSP selection, automated space management policies, and/or file weight calculations in automatic space management.

recall

  To request that a migrated file's data be moved back (unmigrated) onto the file system disk, either by explicitly entering the `dmget(1)` command or by executing another command that will open the file, such as the `vi(1)` command.

regular file

  DMF considers a regular file to be one with no bfid and no offline copies.

snapshot

  The information about all bfid sets that is collected and analyzed by `dmaudit(8)`. The snapshot analysis is available from the `report` function.

soft-deleted database entry

  A daemon database entry for which the MSP copy of the data is no longer valid. Data remains on the alternate media until the database entry is hard-deleted. See also active database entry and hard-deleted database entry.

sparse tape

  A tape containing only a small amount of active information.

special file

  UNIX special files are never migrated by DMF.

state field

  The field in the inode that shows the current migration state of a file.

tape block

  See block.

tape chunk

  See chunk.

task

  A process initiated by the DMF event mechanism. Configuration tasks that allow certain recurring administrative duties to be automated are defined with configuration file parameters.

unmigratable file

  A file that the daemon will never select as a migration candidate.

unmigrate

  See recall.

unmigration file

  A special file created in the user file's file system by the DMF daemon when a file is recalled. The unmigration file holds the data pointers until the MSP process successfully copies the file's data back onto the file system disk from the alternate media; when the copy is complete, the daemon moves the data pointers from the unmigration file inode back into the user file's inode.

unmigration directory

  A directory in which unmigration files are stored.

voided bfid-set state

  A bfid-set state that consists of one or more soft-deleted daemon database entries, either incomplete or complete. There is no user file.

voiding the bfid

  The process of removing the bfid from the user file inode and soft-deleting all associated database entries.

VOL records

  The volume (VOL) records in the tape MSP database that contain information about each tape volume that exists in the pool of tapes used by the tape MSP.

volume merging

  The mechanism provided by the tape MSP for copying active data from volumes that contain largely obsolete data to volumes that contain mostly active data.

zone

  A logical grouping of chunks. Zones are separated by file marks and are the smallest block-addressable unit on the tape volume. The target size of a zone is configurable by media type.

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