The most information about the transaction audit trail in an online application can be obtained by reviewing the system/process flowchart. A system/process flowchart is a diagram that illustrates the sequence of steps, activities, or events that occur within or affect a system or process. A system/process flowchart can provide the most information about the transaction audit trail in an online application, by showing how transactions are initiated, processed, recorded, and completed, and identifying the inputs, outputs, controls, and dependencies involved in each transaction. File layouts are specifications that define how data are structured or organized on a file or database. File layouts can provide some information about the transaction audit trail in an online application, by showing what data elements are stored or retrieved for each transaction, but they do not provide information about how transactions are executed or tracked. Data architecture is a framework that defines how data are collected, stored, managed, and used within an organization or system. Data architecture can provide some information about the transaction audit trail in an online application, by showing what data sources, models, standards, and policies are used for each transaction, but they do not provide information about how transactions are performed or monitored. Source code documentation is a description or explanation of the source code of a software program or application. Source code documentation can provide some information about the transaction audit trail in an online application, by showing what logic, algorithms, or functions are used for each transaction, but they do not provide information about how transactions are handled or audited.