Web-aware application programs can produce an entity body
formed from a CICS® document or from a buffer
of data.
Before you begin
CICS documents can be used as the entity body
of an HTTP message. Use the EXEC CICS DOCUMENT
commands to create them. They can be populated by data specified directly
by the application program, and by document templates, which are portions
of documents defined as CICS resources or created by another CICS program.
You can store documents and document templates for reuse.
Alternatively,
you can specify a buffer of data created by the application program.
You might find this option more convenient for short or simple entity
bodies, and you must use this option for chunked transfer-coding for
the message. However, data created in this way cannot be stored for
reuse so easily.
Procedure
- To create a CICS document, follow the instructions
in Creating a document .
Use the EXEC CICS DOCUMENT application programming
interface (EXEC CICS DOCUMENT CREATE, INSERT, and SET commands)
to create the document. Use the DOCTOKEN option on the WEB SEND command
to specify the document token for the finished document. CICS retrieves
the document and performs appropriate code page conversion, depending
on the options you specify on the WEB SEND command.
The
body of a chunked message cannot be formed from CICS documents.
- Alternatively, assemble a message body in your application
program.
Use the FROM option on the WEB SEND command to
specify the buffer of data.
The size of the data buffer
has no set maximum limit, but you must consider the following factors
that might limit its size in practice:
- The EDSA limit for the CICS region.
- The number of other message bodies that you might be assembling
at the same time in the CICS region. Scheduling constraints
might be imposed by the MAXACTIVE setting for any transaction class
definitions that apply to CICS web support transactions.
- The type of code page conversion used for the message body. For
conversion from the EBCDIC code page 037 to the ASCII code page ISO-8859-1, CICS overwrites
the same buffer of data, so no additional storage is used. For any
other type of code page conversion, CICS requires
additional storage to contain the converted message body. Depending
on the character sets used, the size of this additional storage area
can range from the same size as the original message body, to a theoretical
maximum of four times the size of the original message body (which
is unlikely). For example, a 2 MB buffer of data sent using the FROM
option requires at least 4 MB of storage in total. Double-byte character
sets (DBCS) or multi-byte character sets are likely to require larger
storage areas within this range.