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

• Can be accessed using the 64-bit APIs such as creat64() and open64() only. Depending
on the compilation environment, the 32-bit APIs can be automatically mapped to the 64-bit
APIs. The utilities operators use have been enhanced to support large files. Only application
programmers must be aware of which APIs to use for large files.
• Cannot be restored to systems running RVUs that do not support OSS files larger than
approximately 2 gigabytes.
• If OSS APIs are used, large files cannot be accessed from systems running RVUs that do not
support OSS files larger than 2 gigabytes. However, Guardian Enscribe APIs with 64-bit
elections can access these files.
Fileset Size Considerations
OSS files reside in filesets. A fileset can contain up to 500,000 files as a practical limit.
Filesets reside on disk volumes that are grouped into storage pools. Each fileset has its own storage
pool of one or more disk volumes. A fileset can span multiple disk volumes.
As a storage pool’s disk volumes are filled, you can add more volumes to the pool to accommodate
the files in that fileset. Up to 20 disk volumes can be specified as current members of a storage
pool by including them in the storage-pool file for the fileset; the current members of a storage pool
are sometimes called the creation pool, to contrast them with all of the disk volumes used by the
fileset as a pool for file storage.
Fileset size depends mainly on the type and complexity of the application mix running on your
system. If you are porting an application from another system, you would have some idea of the
application’s requirements and could use that as a basis for estimating the application’s disk-space
requirements on the NonStop system.
OSS Configuration Files
The OSS file system gets configuration information from the ZOSSFSET file and storage-pool files
. You configure the OSS file system by updating these files according to directions in “Managing
Filesets” (page 140).
The ZOSSFSET File
The names of all filesets defined on the system and information about the disk storage they use
resides in a file named ZOSSFSET, defined in the Guardian environment. The ZOSSFSET file is
completely described under “Configuration Files” (page 100).
When a fileset is mounted, its OSS name server accesses catalog files in the catalog volume that
you specify for the fileset in the ZOSSFSET configuration file.
Within that catalog volume, the OSS name server for that fileset uses a Guardian subvolume whose
name begins with ZX0. This name is a reserved subvolume name used only by an OSS name
server.
In this subvolume, the OSS name server for the fileset accesses (and creates if necessary) the catalog
files PXINODE, PXLINK, and PXLOG. Thereafter, whenever someone mounts or remounts a fileset,
the OSS name server that manages that fileset uses these catalog files. Each fileset has a volume,
called a catalog volume, that contains these catalog files and other information about the fileset.
Files in subvolumes whose names begin with ZYQ are subject to special access restrictions. You
cannot access these files from the Guardian environment, and you cannot create new files in these
subvolumes from the Guardian environment.
Storage Pools and Storage-Pool Files
A storage pool is the set of disk volumes on which the OSS data files of a fileset reside. The
storage-pool file is a Guardian EDIT file that determines which disk volumes of the storage pool
can be used for creating new OSS data files that are being added to the fileset. The disk volumes
Relating OSS Files, Filesets, and Disk Volumes 87