The isolation level specifies how transactions that modify the database are handled. By default, the default object gateway is used. Not all types of databases support each isolation level. Some database vendors use different names for the isolation levels.
If you need specific queries to run with different isolation levels, you must define different database connections.
For OLAP data sources, including SAP BW, the isolation level is read-only.
The following isolation levels are in increasing order of isolation:
Read Uncommitted
Changes made by other transactions are immediately available to a transaction.
Database type | Equivalent isolation level |
Oracle | Not applicable |
DB2 | Uncommitted read |
MS SQL Server | Read uncommitted |
Sybase Adaptive Server Enterprise | Read uncommitted |
Informix | Dirty read |
Read Committed
A transaction can access only rows committed by other transactions.
Database type | Equivalent isolation level |
Oracle | Read committed |
DB2 | Read stability |
MS SQL Server | Read committed |
Sybase Adaptive Server Enterprise | Read committed |
Informix | Committed read |
Cursor Stability
Other transactions cannot update the row in which a transaction is positioned.
Database type | Equivalent isolation level |
Oracle | Not applicable |
DB2 | Cursor stability |
MS SQL Server | Not applicable |
Sybase Adaptive Server Enterprise | Not applicable |
Informix | Cursor stability |
Reproducible Read
Rows selected or updated by a transaction cannot be changed by another transaction until the transaction is complete.
Database type | Equivalent isolation level |
Oracle | Not applicable Execute the statement, "SET TRANSACTION READ ONLY," prior to starting a transaction |
DB2 | Repeatable read |
MS SQL Server | Repeatable read |
Sybase Adaptive Server Enterprise | Repeatable read |
Informix | Repeatable read |
Phantom Protection
A transaction cannot access rows inserted or deleted since the start of the transaction.
Database type | Equivalent isolation level |
Oracle | Not applicable |
DB2 | Not applicable |
MS SQL Server | Not applicable |
Sybase Adaptive Server Enterprise | Not applicable |
Informix | Not applicable |
Serializable
A set of transactions executed concurrently produces the same result as if they were performed sequentially.
Database Type | Equivalent isolation level |
Oracle | Serializable |
DB2 | Not applicable |
MS SQL Server | Serializable |
Sybase Adaptive Server Enterprise | Serializable |
Informix | Not applicable |