You can start a transaction by calling the trnBegin method from a CUP.

The range of a global transaction is from the time the trnBegin method is called to the time a synchronization point is acquired (commit). Once you call the trnBegin method, you cannot call another trnBegin method within the same global transaction. When an RPC is issued to an SPP from a CUP, the CUP becomes a root transaction branch and the SPP to which the RPC was issued is executed as a transaction branch. The following figure shows the relationships between a transaction and an RPC when Y is specified for the dcrapautoconnect operand of the TP1/Client/J environment definition.

Figure 2-11 Relationships between a transaction and an RPC (when Y is specified for the dcrapautoconnect operand)