When you use a COMMAREA, the maximum length of the request message
with all the headers is 33,272 bytes. Each header in the request message has
a field that indicates what data structure or application data format comes
next in the request message.
The headers that should be included in the request message depend
on the interface that the service requester is using to invoke the adapter
service. You also need to provide additional headers if you want to invoke
a CICS application using passthrough processing and the Link3270 bridge.
- If you want the service requester to invoke an adapter service
using a CICS-supplied interface, such as the EXEC CICS LINK API
command, include the DFHMAH header structure and the application data in the
COMMAREA. The DFHMAH header describes the structure of the application
data.
- If you want the service requester to utilize the CICS® Transaction
Gateway (CTG) interface, the request message should contain the 101-byte CTG
header, followed by the DFHMAH message header and then the application data.
- If the service requester is an WMQ-enabled application, and you
want to invoke an adapter service, the request message should include a WMQ
header (MQMD), the WebSphere MQ CICS Bridge header (MQCIH), the DFHMADPL stub
program header, and the message header DFHMAH.
The MQCIH header
is only required when you are implementing password authentication. However,
it should always be included because this enables compatibility with future
releases of CICS Service Flow Runtime.
If an error occurs in the WebSphere® MQ-CICS bridge, the MQCIH structure is
returned to the service requestor. This process occurs regardless of whether
the structure was sent in the request message.
The following figure
illustrates the structure of this request message.
- If you want the service requester to use a CICS-supplied interface
or the CTG to invoke a CICS application using passthrough processing, include
the DFHMAH and DFHMAH2 headers followed by the application data.
- If the service requester is an WMQ-enabled application, and you
want to invoke a CICS application using passthrough processing and the Link3270
bridge mechanism, the request message should include a WMQ header (MQMD),
the WebSphere MQ CICS Bridge header (MQCIH), the DFHMADPP stub program header,
the message header DFHMAH, and the message header DFHMAH2. In addition, the
screen header CIA-SCREEN-HEADER and the map header CIA-MAP-HEADER must be
included after the DHMAH2 header.
The following figure illustrates
the structure of this request message.