Transaction management in opcode

Hi,

Here is my requirement:

I have a custom opcode C1, which opens a new readwrite transaction and calls OOTB opcodes. At the end of processing, commits/aborts the transaction, it created.

Now another custom opcode C2, opens a transacation calls C1 and other OOTB opcodes. At the end of processing, commits/aborts the transaction, it created.

Question:

How to change, C1 and C2, such that C1 creates new transaction or uses open transaction and commits its only if its the creator of the transaction.

I guess this is how OOTB opcodes supports transaction handling.

Thanks

Sowmya