Command Area
In the mainframe context, a Command Area refers to a designated input field or buffer where users or programs enter commands for execution by the operating system (z/OS), a subsystem (like CICS, DB2, IMS), or an application. It serves as the primary interface for instructing the system or an application to perform specific actions. The Command Area, often referred to as the Command Line or Command Input Field, is a designated interactive screen area, typically a single line, where a user enters commands, options, or selections to interact with a mainframe system or an application running on it. It serves as the primary interface for direct user input in environments like TSO/ISPF and CICS.
Key Characteristics
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- Interactive Input: Often a specific line or field on a terminal screen (e.g., the
COMMAND ===>line in ISPF) where users type commands. - Programmatic Access: Can also be a memory buffer or parameter list where applications construct and pass commands to system services or other programs.
- Context-Sensitive: The commands accepted and their interpretation are typically dependent on the active environment or application (e.g., ISPF commands, CICS transaction IDs, DB2 SQL statements).
- Command Stacking: Many interactive command areas support entering multiple commands separated by a delimiter (e.g., semicolon
;) for sequential execution. - History and Recall: Interactive command areas often provide functionality to recall previously entered commands, aiding productivity and reducing re-typing.
- Security Integration: Command execution is generally subject to security checks (e.g., RACF) to ensure the user or program has the necessary authorization.
- Interactive Input: Often a specific line or field on a terminal screen (e.g., the
Use Cases
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- TSO/ISPF: Entering z/OS system commands (e.g.,
D U,ALL,ALLOC FI(DD1) DA('MY.DATASET') SHR), ISPF commands (e.g.,SWAP,SPLIT), or application commands directly on theCOMMAND ===>line. - CICS Terminal: Typing a transaction ID (e.g.,
CECI,CEMT) or an application-specific command into the terminal input buffer to initiate a CICS transaction or perform an action. - DB2 Interactive SQL (ISPF DSN): Entering SQL statements (e.g.,
SELECT * FROM SYSIBM.SYSTABLES;) or DB2 commands (e.g.,-DISPLAY DDF) within the DB2I command line. - IMS Terminal: Inputting IMS commands (e.g.,
/DIS PGM) or transaction codes to interact with the IMS database or transaction manager. - JCL
COMMANDParameter: While less common for interactive use, theCOMMANDparameter on aJOBorEXECstatement can specify a system command to be executed during batch job processing.
- TSO/ISPF: Entering z/OS system commands (e.g.,
Related Concepts
The Command Area is intrinsically linked to TSO/ISPF, serving as the primary user interface for interactive z/OS sessions. It facilitates interaction with z/OS system commands and various subsystems like CICS, DB2, and IMS, where specific command sets are processed. It relies on terminal emulation for user input and output, and its functionality is often secured by RACF or other security managers that control command authorization. The concept underpins automation scripts written in REXX or CLIST that simulate user input to execute commands programmatically.