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.

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