DBMaker 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-DBM-COMMIT-ON-BEGIN to a non-zero value. This causes each COBOL START TRANSACTION to first issue a COMMIT. 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, then a COBOL ROLLBACK may affect file I/O that occurred before the most recent COBOL START TRANSACTION. While the default value is "0", this configuration variable can also take values of "Yes," "No," "True," "False," "On," or "Off."