IsolationLevel refers to the degree of concurrency allowed when multiple transactions try to access the same data. In the data source, the isolation level is represented by the number shown after the isolation level name in parentheses. For example, if the currently-configured isolation level is for Repeatable Read, the data source summary will show "IsolationLevel=4".
Below is a list of isolation levels that you can set for DB2.
|
Isolation Level |
Description |
|
Repeatable Read (4) |
Ensures that any row read during a unit of work can not be changed by other application processes until the unit of work has completed. Also ensures that any row changed by another application process cannot be read until it has been committed. At this level, a process is completely isolated from the effects of concurrent application processes. |
|
Serializable (8) |
Ensures that any row changed by another application process cannot be read until it is committed by that application process. Ensures only that the current row of every updateable cursor is not changed by other application processes. Rows read during a unit of work can be changed by other application processes. |
|
Read Committed (2) |
Similar to Repeatable Read in that a unit of work cannot be changed by another process until it has completed and a row changed by another application process cannot be read until it has been committed. However, with Read Committed, an application process that executes the same query more than once may see newly committed rows inserted by another application process that were not present in the original read. |
|
Read Uncommitted (1) |
For a SELECT INTO, FETCH with a read-only cursor, subquery, or subselect used in an INSERT statement, allows any row read during the unit of work to be changed by other application processes and any row changed by another application process to be read even if the change has not been committed by that application process. For other operations, behaves like Read Committed. |
|
None (0) |
No isolation of concurrent application processes. |
|
<Default> |
The default is host platform-dependent. The default for DB2 UDB for iSeries is None so that the driver can access non-journaled files. For all other platforms the default is Read Committed. |