1. A computer program product for performing a transaction in a transactional memory environment for performing transactional executions, wherein memory store data of the transaction are committed to memory at transaction completion, the transactional memory environment comprising a digest-generating transaction to generate a computed digest and a digest-checking transaction to compare computed digests, 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: identifying, by a computer system, a first indicator, the first indicator signaling a beginning instruction of a digest-generating transaction comprising a first plurality of instructions, the digest-generating transaction suppresses committing memory store data of the digest-generating transaction to memory; generating, by the computer system, a first computed digest based on the execution of at least one of the first plurality of instructions; identifying, by the computer system, a second indicator associated with the first plurality of instructions, the second indicator signaling an ending instruction of the digest-generating transaction comprising the first plurality of instructions, wherein the first computed digest is replicable for an error-free execution of the first plurality of instructions; saving, by the computer system, the first computed digest, as a reliability digest, based on completing the digest-generating transaction; not saving the first computed digest based on an abort of the digest-generating transaction; identifying, by the computer system, a third indicator, the third indicator signaling a beginning instruction of a digest-checking transaction comprising a second plurality of instructions, and where the first plurality of instructions and the second plurality of instructions execute in parallel on different threads, memory conflicts between the first plurality of instructions and the second plurality of instructions are suppressed; generating, by the computer system, a second computed digest based on execution of at least one of the second plurality of instructions; identifying, by the computer system, a fourth indicator associated with the second plurality of instructions, the fourth indicator signaling an ending instruction of the digest-checking transaction comprising the second plurality of instructions, wherein the second computed digest is replicable for an error-free execution of the second plurality of instructions; comparing, by the computer system, the second computed digest with the saved reliability digest; based on the second computed digest being equal to the reliability digest, completing the digest-checking transaction and committing the memory store data of the digest-checking transaction to memory; and based on the second computed digest being not equal to the reliability digest, aborting the digest-checking transaction.