Open System Services Management and Operations Guide (G06.29+, H06.07+)

Understanding the OSS File System
Open System Services Management and Operations Guide—527191-005
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Relating OSS Files, Filesets, and Disk Volumes
Guardian disk files are referenced using the OSS filenames in the /G directory. Only
Guardian disk files that are not on disk volumes administered through SMF are visible
in the /G directory.
Guardian disk files on optical disks are visible in the /G directory but cannot be read
from or written to through the OSS file system.
For information on accessing files in the /G directory, see the Open System Services
User’s Guide.
Relating OSS Files, Filesets, and Disk Volumes
You perform OSS file-system configuration and administration tasks through the
Guardian environment. To do these tasks, you need to consider:
•
The sizes of the files your site might use
•
The sizes of the filesets your site might use
•
How your OSS configuration files are used
OSS File Size Considerations
An individual OSS file cannot span multiple volumes. In the OSS environment, a single
file is always stored on just one disk. While a user cannot extend an existing file for
which no more room is available, the user can readily open a new file in the same
directory on another disk.
On H-series RVUs prior to H06.06 and on G-series RVUs prior to G06.29, OSS files
had a size limit of approximately 2 gigabytes, and an underlying Guardian file of
Format 1 (the file format was normally not visible to customer applications). For
H06.06 and later RVUs and G06.29 and later G-series RVUs, OSS files are either
small files or large files.
Small Files
These OSS files:
•
Have an underlying Guardian file format of either Format 1 or Format 2. This
underlying file format is normally not visible to customer applications.
•
Have a size limit of approximately 2 gigabytes when opened or created using a
32-bit API. For information about the exact size limits, see Appendix E,
Environment Limits.
•
Can be accessed using the existing 32-bit application programmatic interfaces
(APIs) such as creat( ) and open( ) in addition to the 64-bit APIs such as
creat64( ) and open64( ). If the file is accessed using a 64-bit API:
°
The file is automatically converted to use an underlying Guardian file format of
Format 2.