TIsolationLevel Enumeration

Specifies the extent to which all outside transactions interfere with the subsequent transactions of the current connection.




TIsolationLevel = (ilReadCommitted, ilReadUnCommitted, ilRepeatableRead, ilIsolated, ilSnapshot);


Value Meaning
ilIsolated The most restricted level of transaction isolation. Database server isolates data involved in current transaction by putting additional processing on range locks. Used to put aside all undesired effects observed in the concurrent accesses to the same set of data, but may lead to a greater latency at times of a congested database environment.
ilReadCommitted Sets isolation level at which transaction cannot see changes made by outside transactions until they are committed. Only dirty reads (changes made by uncommitted transactions) are eliminated by this state of the isolation level. The default value.
ilReadUnCommitted The most unrestricted level of the transaction isolation. All types of data access interferences are possible. Mainly used for browsing database and to receive instant data with prospective changes.
ilRepeatableRead Prevents concurrent transactions from modifying data in the current uncommitted transaction. This level eliminates dirty reads as well as nonrepeatable reads (repeatable reads of the same data in one transaction before and after outside transactions may have started and committed).
ilSnapshot Uses row versioning. Provides transaction-level read consistency. A data snapshot is taken when the snapshot transaction starts, and remains consistent for the duration of a transaction.

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