DBMS_SCHEDULER Job dependency Problem

  I have a question about DBMS_SCHEDULER. I have created two chains, chain_A and chain_B. Created two jobs as job_type CHAIN - Job_A for chain_A and Job_B for chain_B.

I want to make sure that Job_A should not start if Job_B is running and Job_B should not start if Job_A is running.

But no job is dependent on each other that means if Job_A is finished then Job_B need not be started and if Job_B is finished then Job_A need not be started.

And as these jobs are not dependent on each other, they cannot be in the same chain steps, they need to be defined in different chains as the