CMDSTR - Command String

Key Characteristics

• • Literal Text Representation: It is the exact sequence of characters that constitutes a command, as if it were typed at an operator console, TSO prompt, or within a subsystem's command interface.
  • Programmatic Execution: CMDSTRs are primarily used when a program (e.g., REXX, COBOL, PL/I, Assembler) or a batch job needs to issue a system or subsystem command automatically.
  • Interface Dependence: The mechanism for passing and executing a CMDSTR varies depending on the command's target; for example, SVC 34 for MVS commands, IKJEFT01 for TSO commands, or specific APIs for CICS, DB2, or IMS.
  • Security Context: Commands issued via a CMDSTR are subject to the same security checks (e.g., RACF) as manually entered commands, based on the authority of the issuing address space or user ID.
  • Dynamic Construction: In scripting languages like REXX, CMDSTRs can be dynamically built at runtime using variables, allowing for flexible and context-aware command generation.
  • Synchronous or Asynchronous: The execution of a command string can be synchronous (the issuing program waits for completion) or asynchronous (the program continues, and the command executes in the background), depending on the specific interface used.

Use Cases

• • Automated System Operations: A REXX exec or batch program might issue MVS commands like VARY SMS,SMSGROUP,ACTIVATE(groupname) or P jobname to automate the management of system resources or stop tasks.
  • Subsystem Control: A COBOL application or utility could use a EXEC CICS SET PROGRAM(...) ENABLED command string to dynamically control the availability of CICS programs.
  • TSO Command Execution in Batch: Utilizing the IKJEFT01 utility in JCL to execute TSO commands or CLISTs/REXX execs that contain command strings, such as ALLOC FI(DD1) DA('dataset.name') SHR.
  • Database Administration Scripts: A DB2 utility or REXX script might issue DB2 commands like START DATABASE(dbname) or DISPLAY THREAD to manage database objects or monitor activity.
  • IMS Transaction Management: An IMS application or utility could issue IMS commands like /START REGION or /DISPLAY PGM to control IMS regions or programs.

Related Concepts