Abstract
In the two-phase-locking (2PL) model, the data manipulation language operation should need to have a write/read lock before it writes
or reads a data item [86].
In the timestamp-ordering model, a unique timestamp is assigned
to every data manipulation language operation and implements a read
timestamp and a write timestamp for each data item [87]. When a data
manipulation language operation is issued to read or write on the data
item, this operation is allowed only if the read or the write timestamp
of the data item is lower than the timestamp of the data manipulation
language operation; otherwise, the operation will be rejected.