CICS® Web support is a collection of CICS services that enable a CICS region to act
both as an HTTP server, and as an HTTP client. The CICS Internet Guide explains the different components
involved in CICS Web support.
- In each CICS region, the maximum number of concurrent connections between CICS as an HTTP server and Web clients, or between CICS as an HTTP client and a server on the
Web, can in theory be up to 64000. The MXT setting does not directly limit
the number of concurrent connections, because:
- For CICS as an HTTP server, the CWXN transaction (Web attach task) does not
remain in the system for the duration of a persistent connection, but terminates
after each request. This means that between requests, a persistent connection
can exist, being monitored by the Sockets listener task (CSOL), without being
associated with an active task.
- For CICS as an HTTP client, an application program can open and maintain
more than one persistent connection to a server on the Web, and these are
covered by the single active task for the application program.
However, the MXT setting, and any limitations that you set in the transaction
class definitions for CICS Web support transactions, can be used to limit the
amount of CICS Web support activity in the CICS region.
- In practical terms, the number of connections that can be active between
a single CICS region and the Web is primarily limited by the storage available
in the CICS region. Storage requirements for CICS Web support explains the most significant storage
requirements for CICS Web support activities.
- For CICS as an HTTP server, the priority of the various transactions involved
for CICS Web support is significant, and incorrect settings might lead to
a short-on-storage situation. Priorities for CICS Web support transactions (CWXN, CWXU, CWBA) tells you how to set
priorities to avoid issues in this area.
- For CICS as an HTTP server, HTTP responses can be generated by an application,
or provided from a static document, which can be either an HFS file or a CICS document template. A CICS document template can be a variety of
different CICS resources, including a program, a partitioned data set or a file. Relative performance of CICS Web support response methods explains the differences in performance between these response
types.
- If you are using the Secure Sockets Layer (SSL), the security measures
(such as encryption and decryption and the SSL handshake) cause a slight increase
in CPU per transaction. Managing the performance of Secure Sockets Layer support tells you how to manage the
necessary performance impact of these security measures.
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