Chapter 2 HPSS Planning
58 September 2002 HPSS Installation Guide
Release 4.5, Revision 2
• High Availability HPSS configuration
2.5 HPSS Interface Considerations
Thissection describes the user interfaces to HPSS and the various considerations that may impact
the use and operation of HPSS.

2.5.1 Client API

TheHPSS Client API provides a set of routines that allow clients to access the functions offered by
HPSS. The API consists of a set of calls that are comparable to the file input/output interfaces
definedby the POSIX standard (specifically ISO/IEC 9945-1:1990 or IEEE Standard 1003.1-1990), as
well as extensions provided to allow access to the extended capabilities offered by HPSS.
The Client API is built on top of DCE and Encina (which provide threading, transactional RPCs,
and security) and must be run on a platform capable of supporting DCE and Encina client
programs. To access HPSS from client platforms that do not support DCE and Encina clients, the
FTP, Parallel FTP, NFS, Non-DCE Client API, and MPI-IO interfaces can be used.
TheClient API allows clients to specify the amount of data to be transferred with each request. The
amount requested can have a considerable impact on system performance and the amount of
metadata generated when writing directly to a tape storage class. See Sections 2.8.6 and 2.11 for
further information.
The details of the Application Programming Interface are described in theHPSS Programmer’s
Reference Guide, Volume 1.

2.5.2 Non-DCE Client API

The Non-DCE Client API provides the same user function calls as the Client API for client
applicationswho are running on platforms without DCE or Encina with the following exceptions:
• ACL calls are not supported.
• Calls are not transactional.
• It implements its own security interface.
Clientauthentication is performed in one of three ways: remote DCE login, Kerberos authentication
or no authentication (in case of trusted clients). In order to use the NDAPI, the client application
must link the Non-DCE Client API library, and the target HPSS system must have a Non-DCE
Client Gateway server configured and running. The application calls to the library are then sent
overthe network to the NDCG who executes the appropriate Client API calls, returning the results
to the client application. Kerberos must be installed on the client and the gateway in order to use
the Kerberos security feature.