Engine group affinity when switching modes

Engine groups do not exist in threaded mode. When you switch from threaded to process mode, execution classes are assigned to the default engine groups. For example, if you switch from threaded to process mode and then add the Eng_Group execution class and associate it with engine number 3, the default execution classes EC1 and EC2 are associated with the ANYENGINE engine group, and EC3, with the highest engine number, is associated with the LASTONLINE engine group:

sp_showexeclass
classname                      priority   engine_group
              engines
------------------------------ ---------- ------------------------------
              ------------------------------
EC1                                  HIGH                      ANYENGINE
                                         ALL
EC2                                MEDIUM                      ANYENGINE
                                         ALL
EC3                                   LOW                     LASTONLINE
                                           0
Eng_Group                             LOW               new_engine_group
                                           3

When you switch to threaded mode, execution classes lose their engine group affinity and are assigned to syb_default_pool. In threaded mode, the example above becomes:

sp_showexeclass
classname                     priority     threadpool
------------------------------ ----------   ------------------------------
EC1                            HIGH         syb_default_pool
EC2                            MEDIUM       syb_default_pool
EC3                            LOW          syb_default_pool
Eng_Group                      LOW          new_engine_group