Open System Services Management and Operations Guide (G06.30+, H06.08+, J06.03+)

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 J06.03 and later J-series RVUs, H06.06
and later H-series 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 “Environment Limits” (page 411).
• 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.
◦ The file no longer has a size limit of approximately 2 gigabytes. It can grow to the size
limit for large files.
• Can be moved, copied, or restored to systems running RVUs that do not support OSS files
larger than 2 gigabytes. In such cases, if the file has an underlying Guardian file format of
Format 2 but a size of less than approximately 2 gigabytes:
◦ The file is automatically converted to use an underlying Guardian format of Format 1.
◦ The file becomes subject to the file size limit of approximately 2 gigabytes.
Large Files
These OSS files:
• Are larger than approximately 2 gigabytes.
• Have a size limit of approximately 1 terabyte, constrained by the space available on the disk
volume. For information about the exact size limits, see “Environment Limits” (page 411).
NOTE: A pax archive file is limited to 8 gigabytes.
• Have an underlying Guardian file format of Format 2. This underlying file format is normally
not visible to customer applications.
86 Understanding the OSS File System