HSMS offers the user the following basic functions:
Backup
- Version Backup
Archival
Migration
data transfer on magnetic tape cartridges
With each basic function, HSMS provides easy-to-use features for the selection of the files to be processed and for processing control. HSMS is based on the software product ARCHIVE. The functions which were previously called using ARCHIVE are now also available via HSMS.
Backup
Backup is the precautionary creation, storage and management of copies of the data handled in a computer center. These copies can be used to restore data which has been lost. Data loss can be caused by operator errors such as unintentional deletion or by hardware failures.
Data backup and subsequent recovery can be used for reorganizing the data inventory or for migrating IDs to new or other pubsets. In particular, during reorganization especially the splitting of files among several areas (extends) is corrected.
HSMS saves files and job variables logically: files are read from one or more volumes and stored contiguously on other volumes, i.e. they are saved in logical units (refer to section “Data saving in BS2000”, in the “ARCHIVE” manual [2]).
HSMS permits both system backups of the entire data inventory as well as backups of individual applications (e.g. databases). As an option, HSMS saves all the files specified by the user (full backup) or only those files which are new or have been modified since the last backup (incremental backup) and, with large files, only the updated blocks (partial backup).
All types of backup support magnetic tape cartridges and hard disks as target media. HSMS can, for example, dump full backups to magnetic tape cartridge, while the interim incremental backups are written to disk. In addition, backups can be stored intermediately on disk and subsequently, at a convenient time, be moved to magnetic tape cartridges.
By default, only read access is possible to any file currently being saved, i.e. no modifications can be applied during backup. If the function “Concurrent Copy” is activated for backup, files may be modified during backup. This function is particularly useful for applications which should be interrupted either not at all or as little as possible but for which files must nevertheless be backed up.
After a backup to magnetic tape cartridge has been created, this can be automatically duplicated to other magnetic tape cartridges. This increases the security of the data: if a volume is damaged or lost, the copy can be used to reconstruct the corrupted data or restore the lost files.
HSMS also enables backup/restore of pubset copies which were created using SHC-OSD mirroring functions. The Concurrent Copy function is used for this purpose.
Nonprivileged users can back up and restore files and job variables of another user ID of which they are co-owners. For more detailed information on co-ownership, refer to the “SECOS” manual [16].
It is possible to save additional information on the element structure when backing up PLAM libraries (except for the migrated libraries). With the aid of the saved element structure, every element present in the library can be restored individually using the HSMS statement RESTORE-LIBRARY-ELEMENTS.
Version Backup
The version backup is a variant of the backup. HSMS ensures that a number of versions of a file are kept in the version backup archive. The user defines the number of file versions to be kept for a file with the file attribute NUM-OF-BACKUP-VERS (see BS2000 command MODIFY-FILE-ATTRIBUTES). Only differential backups are performed as part of the version backup.
Archival
Archival is the long-term saving of files that are no longer required online at the processing level. It is possible to define retention periods for data that has been archived independently of the retention periods of the volumes.
Archival is used to save storage space at the processing level by virtue of the fact that the files can be deleted after archiving. This also takes some of the load off the catalog. Archival is also used for documentation purposes, e.g. if legal regulations prescribe that data must be retained for specific periods of time.
As with a backup, following archival the data can be automatically duplicated to other magnetic tapes.
Nonprivileged users can also back up and restore files of other user IDs if they are the owners (see the “SECOS” manual [16]).
Migration
The migration function offered by HSMS makes it possible to optimize the utilization of high-speed disk storages. In particular in systems with frequently changing applications it is sound practice to move data that is currently not required (inactive data) from the processing level to a background level, keeping the files accessible via their catalog entries. This helps to avoid pubspace saturation or reaching the user ID-specific pubspace limit without noticeably reducing the availability of the files (can also be automated for pubsets).
Whenever the Data Management System (DMS) attempts to access a migrated file, an HSMS request is generated automatically; the file is then recalled to the processing level without user intervention.
Migration permits more efficient utilization of expensive high-speed external storages without increasing personnel requirements. Since only those pages are migrated which are actually occupied, storage space is saved at the background level in comparison with the processing level.
Files which are stored on the disks of a disk storage system and are mirrored remotely using SHC-OSD should not be migrated if the remote host is unable to access the
S2 processing level.
With the SM2 application the migration and recall activities can be traced and the migration parameters can be set to their optimum values.
Nonprivileged users can also migrate and recall files of which they are co-owners (see the “SECOS” manual [16]).
The basic migration function is not available for files on Net-Storage and private disk, and for files of BS2000-UFS (POSIX) and remote nodes S0 mounted in these.
Data transfer (export/import)
HSMS can be used to transfer files and job variables to other BS2000 systems or other user IDs and to exchange volumes. To do this, the data is written to tape cartridges (exported) and then loaded (imported) to the desired system or user ID. If necessary, you can also work with archive directories.
Moreover, it is possible to transfer only the file catalog entries.
Overview of the HSMS basic functions
BACKUP | ARCHIVAL | MIGRATION | EXPORT |
System service and user control (protection against destruction) | User procedure (company and legal regulations) | System and user control | User procedure |
All files and job variables | Selected files and job variables | Inactive files | Selected files and job variables |
Short-term storage of a copy (e.g. 6 weeks) Version Backup: permanent retention of multiple versions of a file | Long-term storage of a copy (and deletion of the original) | Medium-term swapping out of files | Swapping out for transfer |
RESTORE | RESTORE | RECALL | IMPORT |
In case of loss of the original or for reorganization | In exceptional cases only | For processing | For processing |
Controlled by HSMS statements | Controlled by HSMS statements | Controlled by HSMS statements and automatically when access is attempted | Controlled by HSMS statements |