Isc tpb consistency

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InterBase also supports a restrictive isolation level. isc_tpb_consistency prevents a transaction from accessing tables if they are written to by other transactions; it also prevents other transactions from writing to a table once this transaction reads from or writes to it. This isolation level is designed to guarantee that if a transaction writes to a table before other simultaneous read and write transactions, then only it can change a data of a table. Because it restricts shared access to tables, isc_tpb_consistency should be used with care. However, this mode is serializable, so it meets the highest requirements for transaction consistency. Combined with table reservations, it is also deadlock-free.

A TPB should only specify one isolation mode parameter (and one refinement parameter, if isolation mode is isc_tpb_read_committed). If more than one is specified, later declarations override earlier ones.

If a TPB is declared that omits the isolation mode parameter, InterBase interprets it as isc_tpb_concurrency.