In parallel processing, a blocking function is one that does not return until the function is complete.

disk striping

(1) Multiplexing or interleaving a disk file across two or more disk drives to enhance I/O performance. The performance gain is function of the number of drives and channels used.

file system

(1) The disks located in the fileserver that contain directories. (2) An individual partition or cluster that has been formatted properly. The root file system is always mounted; other file systems are mounted as needed. (3) The entire set of available disk space. (4) A structure used to store programs and files on disk. A file system can be mounted (accessible for operations) or unmounted (noninteractive and unavailable for system use).

The /etc/rc(8) script is the shell procedure that mounts file systems and activates accounting, error logging, and system activity logging. It is a major script that is called by the init(8) command in bringing UNICOS from single-user to multiuser mode. The /etc/rc.local script is provided on UNIX systems to allow site modification of the start-up sequence.

A tree-structured collection of files and their associated data and attributes. A file system is mounted to connect it to the overall file system hierarchy and make it accessible.

logical device

One or more physical device slices that the operating system treats as a single device.

raw I/O

A method of performing input/output in UNIX in which the programmer must handle all of the I/O control. This is basically unformatted I/O. The opposite of "raw I/O" is "cooked I/O" (UNIX humor).


(1) A group of contiguous words or characters that are related by convention. A record may be fixed or of variable length. (2) A record for a listable data set; each line is a record. (3) Each module of a binary-load data set is a record.


A part of the format scheme in disk drives. A disk drive is composed of equal segments called sector; a sector is the smallest unit of transfer to or from a disk drive. The size of a sector depends on the disk drive. See also block.


(1) As used in the context of the low-speed communication (networking) subsystem in an EIOP, a slice is a subdivision of a channel buffer; sections of the buffer are divided into slices used for buffering network messages and data. (2) On CRAY Y-MP, CRAY X-MP EA, and CRAY X-MP systems, a contiguous storage address space on a physical device, specified by a starting cylinder and number of blocks.


(1) A software path of messages related to one file. (2) A stream, or logical command queue, is associated with a slave in the intelligent peripheral interface (IPI) context. The stream is used in identifying IPI-3 commands destined for that slave. A slave may have 0, 1, or many streams associated with it at any given time.


When used in the context of disk software on the IOS-E, unit refers to one disk drive that is daisy-chained with others on one channel adapter. The unit number represents an ordinal for referring to one disk on the channel.