WORM (Write Once Read Many) refers to a storage concept in which data on a WORM volume can be written only once and, after that, cannot be modified or deleted, but can be read any number of times. The ETERNUS CS8000 system provides a WORM feature for Logical Volumes (LVs). BS2000 supports WORM tapes TAPE-U4W from BS2000 V21.0C. MAREN V12.6C and higher provides opportunity to store special WORM volumes attributes: protection period and protection expiration date.
Protection period
The new in MAREN V12.6C volume attribute is kept in MAREN catalog and applicable only for WORM tapes (device type TAPE-U4W). It specifies the period in days when the written WORM tape is to be protected against (administrative) deletion from the pool of volumes in the ETERNUS CS8000. It corresponds to the WORM period of the corresponding logical volume group on the ETERNUS CS. The MAREN Administrator enters the value when adding free WORM volumes in the MAREN catalog (//ADD-FREE-VOLUME) and change it to the actual value of WORM PERIOD in case of its changes in the pool of volumes in the ETERNUS CS8000 by means of //MODIFY-VOLUME-ATTRIBUTES or //MODIFY-TAPE-SET-ATTRIBUTES. The MAREN administrator must perform this synchronization manually; there is no interface between BS2000/MAREN and ETERNUS CS for this purpose. The value specified by MAREN Administrator is used to calculate protection expiration date during writing on the WORM volume. The possible values range is from 1 to 73000. The name of operand corresponding to it in MARENADM statements is PROTECTION-PERIOD.
Protection expiration date
The new volume attribute kept in MAREN catalog applicable only for WORM volumes (device type TAPE-U4W) introduce in MAREN V12.6C. It denotes the date when the protection period is expired and thus the volume can be deleted from the pool of volumes in the ETERNUS CS8000. The value calculated by MAREN automatically when the tape is being written for the first time: current date + protection period defined by MAREN administrator. The protection expiration date is typically calculated at the moment the WORM tape is initialized. For uninitialized WORM tapes, no protection expiration date has yet been assigned. In case MAREN administrator increases protection period for the volume, the value of protection expiration date is recalculated automatically by MAREN. The protection expiration date is stored in MAREN Catalog as ‘YYYY-MM-DD’. If MAREN Administrator keep Protection period in MAREN catalog corresponding to WORM PERIOD value at ETERNUS CS, the protection expiration date correctly shows the date when the WORM volume can be actually deleted from the pool of volumes in the ETERNUS CS8000.
MAREN ensures that the tape is not released after the first write (//FREE-VOLUMES) and that the disk entries of the written WORM tape are not deleted from the MAREN catalog (//DELETE-VOLUME-ENTRY) before the protection period expires (i.e., before the WORM tape can be deleted from the disk pool of ETERNUS CS8000).
The WORM tape attributes PROTECTION-PERIOD and PROTECTION-EXPIRATION-DATE are stored in MARENCAT (the volume catalog) and can be displayed in the MARENADM and MAREN programs using the //SHOW-VOLUME-ATTRIBUTES statement.
MAREN always initializes WORM tapes (TAPE-U4W type volumes) by writing only VOL1 and a duplicate tape label to the WORM tape. When initializing a WORM tape with the INIT utility, the NOHDR option should be used.
WORM volumes cannot be exported or imported. MAREN does not allow them to be marked as exported in the MAREN catalog (//EXPORT-VOLUME) and thus imported (//IMPORT-VOLUME, //IMPORT-FOREIGN-VOLUME).
There is no dependency between the protection expiration date and the release date or expiration date of a WORM volume.
Restrictions of pilot version of MAREN V12.6C:
New media must be initialized before first use. During initialization, the protection period preconfigured for WORM volumes of a volume group in the ETERNUS CS is activated. Until the protection period has expired or the protection expiration date has been reached, it is not possible to delete the tape in the ETERNUS CS.
In MAREN, the protection period or the protection expiration date is only calculated when the tape is opened for writing and data is written, for example as part of a save. It is therefore recommended to initialize volumes only shortly before their use, so that the protection expiration date displayed in MAREN matches the protection period in the ETERNUS CS.
This restriction will be removed with the general customer release as part of SP 26.1. From then on, MAREN will be able to calculate the protection expiration date during tape initialization and thus determine it automatically and correctly.
In general, it is recommended to write to the WORM volume promptly after initialization so that the protection period covers the user’s planned usage timeframe. As usual, the user controls data retention via the expiration date or the retention period. The user has no influence on the protection period in the ETERNUS CS.