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CB (Control Block)

  • These are blocks of storage/memory that describe entities on the system (users, tasks, jobs, etc…).

CEC (Central Electronics Complex)

  • This term is used to refer to the entire z/OS box.

CF (Coupling Facility)

Though different in terms of archiecture and use case, this can be thought of as being analogous to Kubernetes in the sense that they both enable centralized management and resource sharing in an environment composed of otherwise logically independent resources.

  • This is mechanism for enabling resource sharing between disparate z/OS systems. More specifically, it is used to link separate z/OS systems into one optimized system.

CICS (Customer Information Control System)

  • z/OS product for managing online transactions. This product enables fast transactions with high degree of data integrity.


  • In RACF, this is a mechanism for categorizing types of resources to be protected by RACF profiles.

CLIST (Command List)

  • This is like the TSO version of a shell script. This is just a list of TSO commands to run.

COMP (Component)

If you compare z/OS to an application built using microservices, the microservices can be thought of as analogous to z/OS components.

  • A distict piece of the operating system.

Control Instructions

  • These are assembly language instructions that only intended for use by programs running as part of the operating system.

Couple Data Set

  • This is a data set managed by the coupling facility in a sysplex that can be shared by all or some of the z/OS systems in the sysplex.

CP (Central Processor)

  • This term term is used to refer to a general purpose mainframe processor that is not specialized or delegated for running any particular type of workload.

CPACF (CP Assist for Cryptographic Functions)

  • This is specicailized cryptographic hardware built into mainframe processors that allow fast and low cost encryption to be done on the processor. This mechanism is used to enable pervasive encryption.

CPC (Central Processing Complex)

Think of the motherboard in your PC. It has a CPU socket and a few DIMM card slots. A mainframe has multiple draws that each contain multiple CPU sockets and dozens or DIMM card slots.

  • The draws in the z/OS mainframe box that contain the processors and the DIMM cards.

CSECT (Control Section)

  • This is a low level mechanism for segmenting a link edited program.

CSS (Channel Subsystem)

  • The Channel Subsystem is used to manage the allocation of I/O devices such as disks and tapes to the operating system.

CYL (Cylinder)

This can be thought of as an alternative to bytes in the same way that Farenheit is an alternative to Celcius.

  • This is a metric for measuring the amount of data stored on DASD disks. This unit refers to the physical size of the cylinders on the DASD disk drives.


Think gcc and clang.

  • This is a C compiler.