A channel provides an independent data and control path between I/O devices and memory. Channels are generally known as CHPIDs or PCHIDs.
Control units
A control unit contains logic to work with a particular type of I/O device. Some control units can have multiple channel connections providing
multiple paths to the control unit and its devices.
Multiple allengiance
A technique used to access a single disk drive by multiple systems
TSO/E or TSO
Time Sharing Option/Extensions allow users to create an interactive session with z/OS system.
ISPF
Menu-driven interface for TSO providing access to many of the functions most frequently needed by users.
Data sets
z/OS files
Volume serial
A six character name of a disk or tape volume, such as TEST01.
Device type
A model or type of disk device, such as 3390.
Organization
The method of processing a data set, such as sequential.
Record format
The data is stored in chunks called records, of either fixed or variable length.
Record length
The length (number of characters) in each record.
Block size
If records are joined together to save space, this specifies the length of the block in characters.
Extent
An allocation of space to hold the data. When the primary extent is filled, the operating system will automatically allocate more extents, called secondaries.
Space
Disk space is allocated in units called blocks, tracks, or cylinders
CLIST or command list
A list of commands that is executed as if it were one command. CLIST offers shell script-type processing and is unique to z/OS.
REXX or Restructured Extended Executor
An interpretive command language used with TSO that offers shell script-type processing. It is used on many platforms.
Sequential data set
Record are data items that are stored consecutively.
Partitioned data set
Consists of a directory and members. The directory holds the address of each member, so each member can be accessed directly. Each member consists of sequentially stored records.
Partitioned data sets are often call libraries.
Key sequence data sets
Records are data items that are stored with control information (keys) so the systems can retrieve an item without searching all preceding items in the data set.
Master catalog
Data set that premits access to any of the data sets in the computer system or to other catalogs of data sets. Required to reside on a DASD that is always mounted and online.
Access method
Technique that is used to store and retrieve data. Access methods have their own data set structure to organize data, system-provided programs (or macros) to define data sets, and utility programs to process data sets.
Commonly used accessed methods are: QSAM (heavily used), BSAM (for special cases), BDAM (becoming obsolete), BPAM (for libraries), and VSAM (used for more complex applications).
ICKDSF
An utility program used to initialize a DASD volume. ICKDSF can also scan a volume to ensure that it is usable, can reformat all the tracks, can write home addresses, as well as other functions.
Naming data sets
Segments or qualifiers are limited to 8 characters, the first of which must be alphabetic (A to Z) or special (#, @, or $). The remaining seven characters are either alphabetic, numeric (0-9), special, or a hyphen(-).
Name segments are separated by a period(.). Including all name segments and periods, the length of the data set name must not exceed 44 characters. A maximum of 22 name segments can
make up a data set name.