Resolution:
Use of the Data Object Broker (DOB) SRBMODE=Z option combined with a heavy instantaneous usage of clients using the Remote CLI interface (RCLI) may cause the Execution Environment (EE) to hang if insufficient Interpreter class tasks are defined.  


Environment:
============
* SRBMODE=Z specified for the DOB
* TIBCO Object Service Broker for z/OS 5.2.0
* use of RCLI clients including TIBCO BusinessWorks™ OSB Plug-in
* z/OS

Symptoms:
=========
User sessions will hang and no further logons will succeed to the affected EE. The EE will be unusable.

Cause:
======
When a RCLI session begins, TCB affinity may be established at a certain point in processing requiring that the unit of work execute under a particular z/OS TCB. This is to ensure that resources acquired by the session can be successfully used and eventually released back to z/OS. In addition, internal Object Service Broker locks are taken to perform functions safely without interference from other tasks. Accessing the RULES index is one example which requires a shared lock on resource "RULESYSI". If TASKEXECNUM is insufficient and a surge of sessions begin execution, there may be enough sessions to saturate all available Interpreter tasks. With some sessions in a TCB affinity wait on the locked resource and the holder not requiring TCB affinity, the holder of the lock may not be able to be dispatched to free the lock to other waiting Interpreter tasks, creating a deadlock situation.

The second part of this issue involves SRBMODE=Z. This options allows the DOB to process queries very quickly using any available zIIP processor rather than dispatching the work to normal z/OS Query task TCBs. The response can be received from the DOB query request before the original EE request to the DOB is fully completed. This changes the timing of events in the EE. Certain customer configurations have shown that parameter settings that worked successfully under OSB 5.0.0, which did not support zIIP processing, fail with the above described deadlock if run under OSB 5.2.0 with SRBMODE=Z.

Resolution:
===========
If you encounter this situation, the solution is to configure more Interpreter TCBs. This can be done by increasing the TASKEXECNUM parameter in your EE. With increased numbers of TCBs, any session holding a LOCK can be redispatched to allow other waiting sessions to acquire the lock.

References:
===========
TIBCO® Object Service Broker for z/OS Installing and Operating Software Release 5.2.0
TIBCO® Object Service Broker Parameters Software Release 5.2.0

Use of SRBMODE=Z and saturation of Execution Environment INTERP tasks can cause session hang