Technical data

Managing Storage Media
9.1 Understanding Storage Media Concepts
9.1.1.4 The ISO 9660 Standard for CD–ROMs
The OpenVMS implementation of On-Disk Structure conforms to the file
structures defined by the ISO 9660 standard. Table 9–5 defines terms related
to the ISO 9660 standard.
Table 9–5 ISO 9660 Terms
Term Description
Volume space Set of all logical blocks on a volume containing information about the
volume.
System area One of two divisions of CD–ROM volume space; includes logical sectors
0 through 15; reserved for system use.
Data area One of two divisions of CD–ROM volume space; includes the remaining
volume space, beginning with logical sector 16.
Two aspects of an implementation are required to support ISO 9660 file
structures in an OpenVMS environment: partially recorded data blocks and
data interleaving.
• Partially recorded data blocks
ISO 9660 files are recorded in the data area of the media, using extents that
consist of blocks. A block might not be filled with data but also might not be
the final block of a file. The OpenVMS implementation of Files–11 ensures
that the system does not treat an unfilled block as the end of the file unless it
actually is the final file block. This is not visible to the user.
• Data interleaving
Within an extent, data is recorded using file units separated by an interleave
gap, which consists of a specified number of blocks. Data interleaving allows
you to control the speed of access to file data.
9.1.2 Extended File Specifications on OpenVMS Alpha Systems
Extended File Specifications allows files with Windows 95 style or Windows NT
style file names and attributes to reside on, and to be managed from, OpenVMS
Alpha systems. Extended File Specifications support can also be selected on a
per-volume basis.
Traditional and Extended File Names
In an Extended File Specifications environment, you can select either of the
following naming styles for file specifications:
• Traditional file names are allowed on both ODS-2 and ODS-5 volumes.
• Extended file names are allowed on ODS-5, but not on ODS-2 volumes.
For detailed definitions of traditional and extended file names as well as
other introductory information about Extended File Specifications, refer to the
OpenVMS Guide to Extended File Specifications.
The following sections describe the current levels of disk, mixed-version, mixed-
architecture, and network support for Extended File Specifications on OpenVMS
systems.
9–8 Managing Storage Media