Technical data

Managing Storage Media
9.1 Understanding Storage Media Concepts
Beginning with OpenVMS Version 7.2, the limits of storage and index file bitmaps
have been increased as follows:
Type of Bitmap Limit
Storage bitmap 65535 blocks
Index file bitmap 4095 blocks
The increased bitmap limits have the following advantages:
• They allow you to use space more efficiently with small files.
• They increase the number of files allowed on a volume to the architectural
maximum of approximately 16 million.
The behaviors of the INITIALIZE and BACKUP commands reflect the larger
bitmap sizes. Refer to the OpenVMS DCL Dictionary for INITIALIZE command
details and the OpenVMS System Management Utilities Reference Manual for
BACKUP utility details.
Message Displayed with Earlier Versions
The following message is displayed on pre-Version 7.2 systems when you attempt
to access a disk that was initialized on a Version 7.2 or later system:
%MOUNT-F-FILESTRUCT, unsupported file structure level
The increased size of the BITMAP field is incompatible with earlier versions of
OpenVMS.
Check the size of BITMAP.SYS on the disk you want to access. If the size is 256
or greater and you want to access the disk from a pre-Version 7.2 system, you
must copy the data to a disk with a BITMAP.SYS that is less than 256 blocks. If
you use the DCL command BACKUP/IMAGE, be sure to use the /NOINITIALIZE
qualifier.
9.1.1.3 Comparison of ODS-1, ODS-2, and ODS-5 Formats
Table 9–4 compares specific characteristics of On-Disk Structure (ODS) Levels 1,
2, and 5.
Table 9–4 Comparison of ODS-1, ODS-2, and ODS-5 Formats
Characteristic ODS-1 (VAX only) ODS-2 ODS-5
File name length 9.3 39.39 238 bytes, including the
dot and the file type. For
Unicode, 236 bytes is 119
characters, including the dot
and the file type.
Character set Uppercase alphanumeric Uppercase alphanumeric
plus hyphen (-), dollar
sign ($), and underscore
(_)
ISO Latin-1, Unicode (refer to
the description in OpenVMS
Guide to Extended File
Specifications.)
File versions 32,767 limit; version
limits are not supported
32,767 limit; version
limits are supported.
32,767 limit; version limits
are supported.
(continued on next page)
9–6 Managing Storage Media