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A schedule is said to be conflict-serializable when the schedule is conflict-equivalent to one or more serial schedules. Equivalently, a schedule is conflict-serializable if and only if its precedence graph is acyclic when only committed transactions are considered. Note that if the graph is defined to also include uncommitted transactions ...
A schedule is conflict-serializable if and only if its precedence graph of committed transactions is acyclic. The precedence graph for a schedule S contains: A node for each committed transaction in S; An arc from T i to T j if an action of T i precedes and conflicts with one of T j 's actions. That is the actions belong to different ...
In databases and transaction processing, two-phase locking (2PL) is a pessimistic concurrency control method that guarantees conflict-serializability. [1] [2] It is also the name of the resulting set of database transaction schedules (histories).
The scheduler is an operating system module that selects the next jobs to be admitted into the system and the next process to run. Operating systems may feature up to three distinct scheduler types: a long-term scheduler (also known as an admission scheduler or high-level scheduler), a mid-term or medium-term scheduler, and a short-term scheduler.
Almost all implemented concurrency control mechanisms achieve serializability by providing Conflict serializability, a broad special case of serializability (i.e., it covers, enables most serializable schedules, and does not impose significant additional delay-causing constraints) which can be implemented efficiently.
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This could be produced by a TO scheduler, but is not recoverable, as commits even though having read from an uncommitted transaction. To make sure that it produces recoverable histories, a scheduler can keep a list of other transactions each transaction has read from , and not let a transaction commit before this list consisted of only ...
The cron command-line utility is a job scheduler on Unix-like operating systems.Users who set up and maintain software environments use cron to schedule jobs [1] (commands or shell scripts), also known as cron jobs, [2] [3] to run periodically at fixed times, dates, or intervals. [4]