| Application Programmer's I/O Guide - S-3695-35 | ||
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This chapter describes the type of storage devices available on UNICOS and UNICOS/mk systems including tapes, solid-state storage device (SSD), disks, and main memory. The type of I/O device used affects the I/O transfer rate.
The UNICOS tape subsystem runs on all UNICOS systems and is designed for system users who have large-scale data handling needs. Users can read or write to a tape with formatted or unformatted sequential Fortran I/O statements, buffer I/O, and the READDC(3F), READP, WRITEC(3F), and WRITEP(3F) I/O routines.
A Fortran program interfaces with the tape subsystem through the Fortran I/O statements and the I/O library. The Tape Subsystem User's Guide, describes the tape subsystem in detail.
There are two different types of tape I/O interfaces: the traditional read[a] and write[a] system calls and tapelist I/O, which is unique to magnetic tape processing on UNICOS and UNICOS/mk systems.
Tapelist I/O allows the user to make several I/O requests in one system exchange. It also allows processing of user tape marks, bad tape data, and end-of-volume (EOV) processing.
The system libraries provide the following four common ways to perform tape I/O:
Through the use of the system calls.
Through the stdio library, which is commonly used from C. This method provides no means to detect or regulate the positioning of tape block breaks on the tape.
Through Fortran I/O (not fully supported on UNICOS/mk systems). This provides bad data handling, foreign data conversion, EOV processing, and high-performance asynchronous buffering. Only a subset of these functions are currently supported through Fortran I/O for the ER90 tape device.
Through the Flexible File I/O (FFIO) system (not available on UNICOS/mk systems). FFIO is used by Fortran I/O and is also available to C users. It provides bad data handling, foreign data conversion, EOV processing, and asynchronous buffering. FFIO uses tapelist I/O. For more information about FFIO see the INTRO_FFIO(3F) man page. Only a subset of these functions are currently supported through Fortran I/O for the ER90 tape device.
The tape subsystem provides the following capabilities:
Label processing
Reading and writing of tape marks
Tape positioning
Automatic volume recognition (AVR)
Multivolume tape files
Multifile volume allocation
Foreign dataset conversion on UNICOS and UNICOS/mk systems
User end-of-volume (EOV) processing
Concatenated tape files
The tape subsystem supports the following user commands on UNICOS and UNICOS/mk systems:
See the Tape Subsystem User's Guide, for more details about the tape subsystem.
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