The COBOL85/COBOL2000 runtime system comprises runtime modules that are used when linking a COBOL85/COBOL2000 object to an executable program.
The COBOL runtime modules can be recognized by their prefix “ITC”. They are available as elements in the following libraries provided that they were not preloaded with the subsystem:
Library for static linkage:
SYSLNK.CRTE (/390 systems)
The COBOL runtime modules are present in object module format (type R).
When static linking is performed with CRTE , all unresolved external references are resolved.
Library for linking with the partial bind linkage method
SYSLNK.CRTE.PARTIAL-BIND and SYSLNK.CRTE.COMPL (/390 systems)
These libraries support the partial bind linkage method which significantly reduces the size of the final linked COBOL programs. In this case, all unresolved references are resolved by linkage modules. The COBOL85/COBOL2000 runtime system is not dynamically loaded until execution time (see section “Libraries for the partial bindlinkage method on /390 systems” f).
The programs linked using the partial bind linkage method use the subsystem COBPART (linkage with SYSLNK.CRTE.PARTIAL-BIND or SYSLNK.CRTE.COMPL).
In the case of COBOL and mixed C/COBOL programs the complete partial bind linkage method (library SYSLNK.CRTE.COMPL) can only be used if the objects run under POSIX and shared objects are loaded.
For more detailed information and examples of the various linkage methods, refer to chapter “Linkage of CRTE”.
Most of the shareable runtime modules are prelinked in a main module named ITCSR85 in the library SYSLNK.CRTE.SHARE, which can be loaded into class 4 memory by the system administrator using the CRTECOB subsystem (see section “Shareability of CRTE”).
The runtime modules represent subprograms known to the COBOL85 or COBOL2000 compiler. They can be divided into two broad groups:
Subprograms for complex COBOL statements
Subprograms for interfacing the generated module to operating system functions
The main purpose of such subprograms is to ensure that code generation of the compiler is completely independent of the operating system.
Important functions in this context are:interface of COBOL programs to the I/O system
interface of COBOL programs to SORT
interface of COBOL programs to UDS
interface of COBOL programs to executive functions
A list with the names and functions of all COBOL85 and COBOL2000 runtime modules is provided in the COBOL User Guides.
Support for large files (> 2 GB) in COBOL programs
COBOL programs compiled with COBOL85 V2.3A or COBOL2000 and linked with CRTE V10.1A are able to process large BS2000 files (> 2 GB).
The maximal size of a BS2000 file is 4096 Gigabyte (= 4 Terabyte), a POSIX file may be maximal 1024 Gigabyte (= 1 Terabyte) in size.