| 摘要 |
<p>A wait depth limited concurrency control method for use in a multi-user data processing environment restricts the depth of the waiting tree to a predetermined depth, taking into account the progress made by transactions in conflict resolution. In the preferred embodiment, the waiting depth is limited to one. Transaction specific information represented by a real-valued function L, where for each transaction T in the system at any instant in time L(T) provides a measure of the current "length" of the transaction, is used to determine which transaction is to be restarted in case of a conflict between transactions resulting in a wait tree depth exceeding the predetermined depth. L(T) may be the number of locks currently held by a transaction T, the maximum of the number of locks held by any incarnation of transaction T, including the current one, or the sum of the number of locks held by each incarnation of transaction T up to the current one.</p> |
