| 摘要 |
<p>The data dictionary manager (85) takes advantage of the computer system's journaling capability enhanced to allow users and application programs to manipulate system objects (65) without the use of the data dictionary's built-in utilities. As used here, journaling capability is an internal tracking facility which exists in a somewhat limited form on many computer systems. Typical journaling mechanisms (38) maintain a repository of information about some of the activities that have taken place on the computer system. The information is usually stored in a record called an audit journal (75). Since many computer systems have limited journaling mechanisms already in place, these mechanisms can be enhanced to add the ability to record information about changes to system objects. Examples of system object changes included in the audit journal are deletes, creates, renames, and moves. Once the information has been logged in the audit journal, the data dictionary manager retrieves the information from the audit journal and ensures that the changes are accurately reflected in the data dictionary (90). Since the audit journal can be made accessible to several processes, it is possible to have different instances of the data dictionary manager responsible for different data dictionaries. Alternatively, it is possible to have a single data dictionary manager that is responsible for all of the computer system's data dictionaries. <IMAGE></p> |
