Technical data

Managing Storage Media
9.1 Understanding Storage Media Concepts
Table 9–4 (Cont.) Comparison of ODS-1, ODS-2, and ODS-5 Formats
Characteristic ODS-1 (VAX only) ODS-2 ODS-5
Directories No hierarchies of
directories and
subdirectories; directory
entries are not ordered
1
Alpha: 255
2
VAX: 8 (with rooted
logical, 16)
Alpha: 255
VAX: 8 (with rooted logical,
16)
System disk Cannot be an ODS-1
volume
Can be an ODS-2
volume
ODS-5 volume not supported
for Version 7.2
Page file, swap
file, dump file,
parameter (.PAR)
file, and other
system files
Supported Supported Not supported
OpenVMS Cluster
access
Local access only; files
cannot be shared across
a cluster
Files can be shared
across a cluster
Files can be shared across
a cluster. However, only
computers running OpenVMS
Version 7.2 or later can
mount ODS-5 disks. VAX
computers running Version
7.2 or later can see only files
with ODS-2 style names.
Disk Unprotected objects Protected objects Protected objects
Disk quotas Not supported Supported Supported
Multivolume files
and volume sets
Not supported Supported Supported
Placement control Not supported Supported Supported
Caches No caching of file
identification slots or
extent entries
Caching of file header
blocks, file identification
slots, and extent entries
Caching of file header blocks,
file identification slots, and
extent entries
Clustered allocation Not supported Supported Supported
Backup home block Not supported Supported Supported
Protection code E E means ‘‘extend’’ for
the RSX–11M operating
system but is ignored by
OpenVMS
E means ‘‘execute
access’’
E means ‘‘execute access’’
Enhanced
protection features
(for example, access
control lists)
Not supported Enhanced protection
features supported
Enhanced protection features
supported
1
RSX–11M, RSX–11D, RSX–11M–PLUS, and IAS systems do not support subdirectories and alphabetical directory
entries.
2
Prior to OpenVMS Version 7.2, RMS limited directory levels to 8 or 16, although PATHWORKS and other programs that
did not use RMS could use unlimited directory depth.
Note
Future enhancements to OpenVMS software will be based primarily on
Structure Levels 2 and 5; therefore, Structure Level 1 volumes might
be further restricted in the future. However, Compaq does not intend for
ODS-5 to be the default OpenVMS file structure. The principal function of
ODS-5 is to enable an OpenVMS system to be a server for other systems
(such as Windows NT) that have extended file names.
Managing Storage Media 9–7