1. At least one hardware computer storage medium comprising computer-executable instructions that, when executed by a computer, cause the computer to: place a set of transactions into one of a plurality of transaction groups; and provide a contention management mechanism configured to detect a conflict between multiple concurrently executing transactions of a plurality of transactions of a program, wherein the set of transactions is from the plurality of transactions, and wherein each of the plurality of transactions is implemented as code configured to access shared memory, and wherein the set of transactions is configured to access data that is disjoint from other data, and wherein others of the plurality of transactions that are not in the set of transactions are configured to access the other data, and wherein each of the plurality of transaction groups is configured to utilize one of a plurality of locking and versioning mechanisms that is incompatible with others of the plurality of locking and versioning mechanisms utilized by others of the plurality of transaction groups, and wherein at least one of the others of the plurality of transaction groups is configured to concurrently utilize at least one of the others of the plurality of locking and versioning mechanisms.