Bind

Program Management

Enhanced Definition

In z/OS, the **bind** process, often performed by the **Linkage Editor** or the **Program Management Binder (PMB)**, is the final step in creating an executable load module or program object from one or more object modules. It combines compiled or assembled program units with necessary library routines and resolves external references, producing a program ready for execution.

Key Characteristics

- Input: Takes one or more object modules (output from compilers like COBOL, PL/I, C/C++, or assemblers) and optionally existing load modules or program objects.
- Output: Produces a load module (stored in a PDS) or a program object (stored in a PDSE), which is the executable form of the program.
- External Reference Resolution: Resolves external symbols (e.g., calls to subroutines, references to common data areas) by locating them in other input modules or specified libraries (e.g., SYSLIB, STEPLIB, LINKLIB).
- Control Statements: Uses Linkage Editor or Binder control statements (e.g., ENTRY, INCLUDE, NAME, ALIAS, SETCODE, ORDER) to direct the binding process, define entry points, create aliases, and structure the output.
- Attributes: Assigns attributes to the load module/program object, such as REUSABLE, REENTRANT, REFRESHABLE, AC, and AMODE, which are crucial for program behavior in shared environments.
- Dynamic Link Libraries (DLLs): When using PDSEs, the Program Management Binder can create program objects that support DLLs, enabling modular application design and shared code segments at runtime.

Use Cases

- Batch Program Execution: Creating executable load modules for COBOL, PL/I, or C/C++ batch applications that will be invoked via JCL.
- Online Transaction Processing (CICS/IMS): Binding application programs (e.g., CICS transactions, IMS message processing programs) that need to be loaded and executed within the respective online environments.
- System Utilities and Services: Linking system-level programs, user exits, or custom utilities that extend z/OS functionality.
- Subroutine Libraries: Combining multiple related subroutines into a single load module or program object for easier management and distribution.
- Creating Shared Libraries: Utilizing the Program Management Binder to create program objects that function as Dynamic Link Libraries for applications to share common code.

Related Concepts

The bind process is a critical post-compilation step, directly following compilation (e.g., COBOL compiler) or assembly (e.g., HLASM assembler), which produce object modules. It precedes program execution, as a program cannot run until it has been bound into an executable format. It relies heavily on JCL for specifying input datasets, output libraries, and binder control statements, and interacts with Program Libraries (PDS/PDSE) where the resulting load modules or program objects are stored.

Best Practices:

Use PDSEs for New Development: Prefer PDSEs over PDSs for program libraries, as PDSEs support program objects, DLLs, and offer better space management and concurrency.
Minimize Load Module Size: Include only necessary object modules and library routines to reduce load module size, improving load time and memory utilization.
Specify Libraries Correctly: Ensure SYSLIB and other DD statements in the JCL point to all necessary object module and