Introduction to CA IDMS Data Manipulation Language › Assembling and Executing Programs

Assembling and Executing Programs

An Assembler source program that contains DML statements is processed by the DML precompiler (IDMSDMLA) before it is submitted to the assembler. The DML precompiler performs the following functions:

• Converts most DML statements into standard Assembler source statements.
• Ensures that all statements issued by the program are consistent with the logical structure of the database, the subschema view of the program, and the access restrictions defined in the subschema.
• Copies information maintained in the dictionary into program storage. Dictionary entities include database record descriptions, file definitions, map records, map definitions, logical records, and other predefined modules.
• Updates the dictionary with compile-time statistics used to monitor database activities for a given application program.
• Performs source level error checking.
• Generates an optional source statement listing of error conditions detected during DML processing.
• Supports the use of native VSAM files in conjunction with database access methods.
• Recognizes record, element, and file synonyms defined in the dictionary.
• Allows programs to be compiled for execution under various TP monitors without changing the source DML statements.

An Assembler program must be submitted to the DML precompiler if the program contains any of the following statements:

• An @COPY IDMS statement
• An @INVOKE statement
• Logical-record DML statement containing a WHERE clause

If none of these statements is included, the Assembler program can bypass the DML precompiler. The source can be submitted directly to the assembler because most Assembler DML statements are macro instructions that are expanded during assembly. It is recommended, however, that all programs accessing the database or running under a DC/UCF system use the DML precompiler. For a list of Assembler DML macros, see the Assembler DML Macros and Error Messages.

Output from the DML precompiler is a card-image source file that serves as input to the assembler. Output from the assembler consists of an object program and a source listing that includes any generated diagnostics. During assembly, most procedural DML verbs are expanded into executable Assembler source code, whether or not the DML precompiler was executed.

After the program is assembled, it is submitted to the linkage editor. The linkage editor link edits the object program into a specified load library. Output from the linkage editor consists of a load module and a link map.

The following figure illustrates the steps involved in assembling and executing an Assembler program containing DML statements.