1. A computer program product for gathering diagnostics during a transactional execution in a transactional memory environment for performing transactional executions, wherein memory store data of a transaction are committed to memory at transaction completion, the computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: beginning, by a computer system, execution of a first transaction that includes a plurality of instructions; generating, by the computer system, a computed digest based on a digest generating algorithm operating on invariant data in at least one of a plurality of instructions executed by the first transaction; beginning, by the computer, execution of a first nested transaction that includes a plurality of instructions, the first nested transaction executed within a transactional region of the first transaction; saving, by the computer, a snapshot of the computed digest as a first nesting level snapshot; updating, by the computer system, the computed digest based on a digest generating algorithm operating on invariant data in at least one of a plurality of instructions executed by the nested transaction; upon completion of the first nested transaction, determining whether the computed digest matches a previously saved computed digest that is based on the digest generating algorithm operating on the invariant data in a previous completion of the first nested transaction; and based on the computed digest not matching the previously saved computed digest: aborting the first nested transaction; restoring the computed digest to the first nesting level snapshot; and restarting the first nested transaction.