Isolation Levels
Isolation levels allow users a balance between consistency and concurrency. This feature makes it possible to increase concurrency when the absolute consistency and accuracy of the data is not essential.
Ingres supports four isolation levels defined by the ANSI/ISO SQL92 standard:
• Read Uncommitted (RU)
• Read Committed (R)
• Repeatable Read (RR)
• Serializable
The highest degree of isolation is Serializable and is the default behavior of Ingres transactions because it offers the highest degree of consistency but the lowest degree of concurrency.
At lower degrees of isolation (such as Read Uncommitted), more transactions can run concurrently, but inconsistencies can occur.
An isolation level is set by using the statements:
SET SESSION ISOLATION LEVEL
SET TRANSACTION ISOLATION LEVEL