Structures

The structures are generated by macros that have various parameters to control the action of the macro. These parameters are described in the following sections.

From time to time new versions of the MQ structures are introduced. The additional fields in a new version can cause a structure that previously was smaller than 256 bytes to become larger than 256 bytes. Because of this, write assembler instructions that are intended to copy an MQ structure, or to set an MQ structure to nulls, to work correctly with structures that might be larger than 256 bytes. Alternatively, use the DCLVER macro parameter or CMQVERA macro with the VERSION parameter to declare a specific version of the structure.

• Specify the name of the structure
  To declare more than one instance of a structure, the macro prefixes the name of each field in the structure with a user-specifiable string and an underscore.
• Specify the form of the structure
  
• Control the version of the structure
  By default, the macros always declare the most recent version of each structure.
• Declaring one structure embedded within another
  
• Specify initial values for fields
  Specify the value to be used to initialize a field in a structure by coding the name of that field (without the prefix) as a parameter on the macro invocation, accompanied by the value required.
• Control the listing
  

Parent topic: System/390 assembler programming