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UPDATE_ISOLATION_LEVEL= |
Default value: | RC |
Alias: | UIL= |
Syntax | |
Details |
Syntax |
UPDATE_ISOLATION_LEVEL=S | RC | RR | V |
S = Serializable | |
RC = Read Committed | |
RR = Repeatable Read | |
V = Versioning |
Details |
The degree of isolation identifies
UPDATE_ISOLATION_LEVEL= is ignored if UPDATE_LOCK_TYPE= is not set to ROW.
The ODBC driver manager supports four isolation levels. The isolation levels are defined in terms of several possible occurrences:
For example, suppose that transaction T1 performs an update on a row, transaction T2 then retrieves that row, and transaction T1 then terminates with rollback. Transaction T2 has then seen a row that no longer exists.
For example, suppose that transaction T1 retrieves a row, transaction T2 then updates that row, and transaction T1 then retrieves the same row again. Transaction T1 has now retrieved the same row twice but has seen two different values for it.
For example, suppose that transaction T1 retrieves the set of all rows that satisfy some condition. Suppose that transaction T2 then inserts a new row that satisfies that same condition. If transaction T1 now repeats its retrieval request, it will see a row that did not previously exist, a phantom.
The isolation levels for UPDATE_ISOLATION_LEVEL= include the following:
These transactions are serializable but higher concurrency is possible than with the Serializable isolation level. Typically, a nonlocking protocol is used.
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