ODBC has no START TRANSACTION method. Everything since the last COMMIT or ROLLBACK is considered part of the current transaction.
To ensure that the previous transaction has been ended before a new one begins, set A_ODBC_COMMIT_ON_BEGIN to a nonzero value. This causes each COBOL START TRANSACTION to first issue a COMMIT to all applicable ODBC drivers in use. This ensures that the previous transaction has been ended before the new one starts.
If this variable is not set, or is set to 0, a COBOL ROLLBACK may affect file I/O that occurred before the most recent COBOL START TRANSACTION. While the default value is 0 (or OFF, FALSE, or NO), this configuration variable can also take values of ON (TRUE or YES).