Define Timestamp ordering

Ans In timestamp-based method, a serial order is made among the concurrent transaction by assigning to every transaction a unique nondecreasing number. The common value assigned to each transaction is the system clock value at the beginning of the transaction, therefore the name timestamp ordering. This value then can be employed in deciding the order in which the conflict between two transactions is resolved. A transaction along with a smaller timestamp value is considered to be an "older" transaction as compared to another transaction with a larger timestamp value.