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

The OSS file-system cache is used to buffer data transfers between the OSS disk files and an OSS
application. Whether this cache is used for a specific file depends on:
• Options used by an application to open the file
• The setting of the OSSCACHING flag for the disk process of the disk volume that contains
that file
For more information on configuring this cache, see“Changing OSS File Caching for the Disks of
a Fileset” (page 155).
Disk processes also can use data caches, as shown in Figure 3 (page 34). The use of disk process
caching determines whether OSS file-system caching can be used, as mentioned above. See the
Storage Subsystem Configuration and Management Manual for additional information about disk
process caching.
An OSS name server also maintains a cache of the most recently resolved names for its filesets.
This cache has a default size of 4096 inode values and 4096 link values. Other cache sizes can
be specified through Subsystem Control Facility (SCF) commands, as described under “Configuring
an OSS Name Server” (page 121).
OSS resources such as the PXS extended segment, data cache, OSS name server inode cache,
and link cache, can also be monitored using Measure. See the Measure Reference Manual for
information about the OSSCPU and OSSNS entities.
An OSS server process (OSP) server named $ZSPnn runs in each processor (nn indicates the
processor number). This server process manages resources for thread-aware file I/O operations
on OSS regular files without blocking threaded client applications from running other threads. The
OSP servers also allow those shared OSS resources to be released without requiring involvement
of the client application when thread-aware I/O operations complete. This illustration shows a
simplified view of the role of the OSP server in a processor:
NOTE: OSP servers are supported on systems running J06.04 and later J-series RVUs and H06.15
and later H-series RVUs only.
Interprocess Communication Facilities
Open System Services provides a set of interprocess communication (IPC) facilities identical to
those of the UNIX operating system. The OSS IPC facilities are separate from the IPC facilities
supplied within the Guardian environment.
OSS IPC facilities include the facilities described in the following subsections:
• “OSS Shared Memory and Semaphores” (page 39)
• “OSS Message Queues” (page 39)
Components to Be Managed 35