MaxDB allows concurrent transactions on database objects. To do this, it uses a lock concept that creates locks on rows and tables to contain individual transactions. The lock operation type plays an important role in this. This is determined by defining an isolation level.
Use the Isolation Level option if you want to change the system default value for the lock operation type (Committed). The value defined in this way then applies for all connections of the data source.
The set lock operation type can be overridden by the application using the function SQLSetConnectAttr and queried with SQLGetConnectAttr.
Overview of the possible lock operation types
Dirty Read |
Non-Repeatable Read |
Phantom Read |
|
x |
x |
x |
|
Committed |
|
x |
x |
Repeatable |
|
|
x |
Serializable |
|
|
|
The lock operation type Uncommitted corresponds to the weakest isolation level (0), while Serializable corresponds to the strongest isolation level (4).
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1. Start the ODBC Data Source Administrator by choosing Start ® Settings ® Control Panel ® Administrative Tools ® Data Sources.
2. Choose Add.
3. Choose the MaxDB ODBC driver and then Finish.
4. Specify the name of the data source, the name of the database instance, and the name of the database server. Choose Options.
5. In the Isolation Levelfield, select the required lock operation type.
6. Confirm the windows until the ODBC Data Source Administrator closes.
The next time that you connect to the database server using this data source, the MaxDB ODBC driver runs with the selected lock operation type.