There are two ways to control transactions through the DB Access Module for DB2 CLI:

• setting isolation levels

• using transaction control methods

Each of these techniques is described below.

2.11.1 Setting Isolation Levels

Table 4: Setting the isolation level

To determine the current isolation level, call RWDBConnection::isolation() without an argument.

2.11.2 Using Transaction Control Methods

You can explicitly control transactions through the following methods of the DB Interface Module:

RWDBConnection::beginTransaction() RWDBConnection::rollbackTransaction() RWDBConnection::commitTransaction()

These methods have straightforward implementations that correspond to the following DB2 functions:

SQLSetConnectAttr(hDbc, SQL_ATTR_AUTOCOMMIT, SQL_AUTOCOMMIT_OFF, 0) SQLEndTran(SQL_HANDLE_DBC, hDbc, SQL_ROLLBACK) SQLEndTran(SQL_HANDLE_DBC, hDbc, SQL_COMMIT)

An application can add the DB Interface Module transaction methods to its code to take explicit control of its transaction blocks. The following code demonstrates how these methods can be used to commit or to rollback transactions:

// Assume we have a table myTable(c int) with no rows in it. RWDBInserter ins= myTable.inserter(); cn1.beginTransaction(); // Begin transaction... (ins << 1).execute(cn1); // First insertion ... cn1.commitTransaction(); // Save first insertion cn1.beginTransaction(); // Begin another transaction (ins << 2).execute(cn1); // Second insertion (ins << 3).execute(cn1); // Third insertion cn1.rollbackTransaction(); // Rollback transaction erasing // second and third insertions. // The above program results in myTable holding one row of data. // Its value is 1.

Please note that nested transactions and savepoint features are not supported by DB2.

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DB2 does not support nested transactions and savepoint features.

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Attempting to create a nested transaction generates a server error. Attempting to use the savepoint features of the DB Interface Module generates the error RWDBStatus::notSupported for the connection that tried.