The connection attributes of a DB2CONN are:
A protected thread is not terminated immediately when it is released. It is terminated only after two completed purge cycles, if it has not been reused in the meantime. Therefore, if the purge cycle is set to 30 seconds, a protected thread is purged 30 - 60 seconds after it is released. The first purge cycle after the attachment facility starts is always 5 minutes. After that the purgecycle values are applied. An unprotected thread is terminated when it is released (at syncpoint or end of task) if there are no other transactions waiting for a thread on that DB2ENTRY. Only threads belonging to a DB2ENTRY can be protected. Pool threads and command threads cannot be protected.
Acceptable characters:
Unless
you are using the CREATE command, any lowercase characters you enter are converted
to uppercase. |
Specifies the maximum number of TCBs that can be used to process DB2 requests. The default is 12. The minimum number is 4 and the maximum is 2000. When connected to DB2 Version 5 or earlier, the CICS DB2 attachment facility creates the TCBs in the form of subtasks up to the limit specified by TCBLIMIT. Each of these subtasks identifies to DB2 and creates a connection into DB2. When connected to DB2 Version 6 or later, CICS creates open TCBs (up to the limit specified by the system initialization parameter MAXOPENTCBS). The TCBLIMIT attribute of the DB2CONN definition governs how many of the open TCBs can be used to access DB2 — that is, how many of them can identify to DB2 and create a connection into DB2.
The TCBLIMIT value controls the total number of threads for the CICS region. For this reason, the recommended value for TCBLIMIT is the sum of all the thread limit values (that is, the sum of all THREADLIMIT attributes on the DB2 connection and DB2 entry resource definitions, plus the COMTHREADLIMIT value on the DB2 connection definition) up to the limit of 2000.
When CICS is connected to DB2 Version 5 or earlier, note that if you specify THREADLIMIT values which, in total, exceed the number of TCBs (TCBLIMIT) that can be created, a task could acquire a thread and then find that there is no available TCB. In this case, the task is suspended, with the INQUIRE TASK command showing HTYPE(CDB2TCB) with no corresponding HVALUE. This contrasts with the case where a task is suspended waiting for a thread, which shows HTYPE(CDB2RDYQ) and HVALUE(*POOL), HVALUE(*COMD), or HVALUE(entry_name), as appropriate.
When CICS is connected to DB2 Version 6 or later, note that if MAXOPENTCBs is exceeded (so no more open TCBs can be created), the task is suspended with HTYPE(DISPATCH) and HVALUE(OPEN_TCB). If MAXOPENTCBs is not exceeded but TCBLIMIT is exceeded , then the task is suspended with HTYPE(CDB2CONN). In this situation, although CICS has an open TCB available, the maximum allowed number of open TCBs are being used to access DB2 (as defined in TCBLIMIT).
When determining the number for TCBLIMIT, you must consider the amount you specified for the MAX USERS parameter on DB2 installation panel DSNTIPE.