A transactional database server is accessible by applications. Applications indicate whether access is made using an online protocol. Where the database server determines that a request received from an application is made using the online protocol, the server will return one of a set of defined error codes upon identified system resources being determined to be scarce. Applications monitor responses from the database server for the defined error codes. On receipt of one of the defined error codes an application will issue a commit to the database server to attempt to release system resources for use by applications.