MAXOPENTCBS
The MAXOPENTCBS system initialization parameter specifies the maximum number, in the range 1 through 4032, of open task control blocks (open TCBs) CICS® can create in the pool of L8 and L9 mode TCBs.
If you do not specify the MAXOPENTCBS parameter the MXT value will be used to set the MAXOPENTCBS parameter.
- MAXOPENTCBS=number
- Within this limit, there are no constraints on how many of the
TCBs in the pool are L8 TCBs, and how many are L9 TCBs.
- L8 mode TCBs are used in the following circumstances:
- For CICSKEY OPENAPI application programs.
- For OPENAPI task-related user exits (TRUEs), for example the CICS-DB2 and WebSphere® MQ Attachment Facilities, and the CICS-DBCTL Database Adapter Transformer (DFHDBAT) when used with IMS Version 12 or later. TRUEs always run in CICSKEY.
- By CICS itself, because CICS uses OPENAPI CICSKEY programs that run on L8 TCBs when accessing doc templates and HTTP static responses that are stored in z/OS® UNIX System Services files, or when processing web service requests and parsing XML. CICS also uses L8 TCBs when authenticating a password, password phrase or kerberos token when the original request was on the QR TCB.
- L9 mode TCBs are used for USERKEY OPENAPI application programs.
Note: If any of the following CICS resources, BUNDLE, DB2CONN, DOCTEMPLATE, MQCONN, PIPELINE, TCPIPSERVICE, or WEBSERVICE, are defined in the resource definition groups that are installed during CICS initialization by the lists specified in the GRPLIST system initialization parameter, then MAXOPENTCBS=3 or greater must be specified.For more information about open TCBs, see Open TCB management.
- L8 mode TCBs are used in the following circumstances: