The main reason for providing support for OPENAPI programs is
to allow you to move application workloads off the QR TCB onto multiple open
TCBs. This allows the possibility of better utilization of machine resources
to achieve better throughput.
Another reason that you might
want to use OPENAPI programs could be to allow the use of other (non CICS®) APIs.
Use
of other APIs is possible because, if an open TCB is blocked by an operating
system wait, then only the single application is affected not the whole of CICS,
which would be the case if they executed under the QR TCB. Such OPENAPI programs
are not permitted to execute on the QR TCB precisely because of this risk
of blocking the TCB by an operating system wait and thus affecting the whole
of CICS.
- Use of other (non CICS) APIs within CICS is entirely at the discretion and
risk of the user. No testing of other (non CICS) APIs within CICS has been undertaken and use of such
APIs is not supported by IBM® Service.