Time Stamps on Disk Pages

Each disk page has one time stamp in the page header and a second time stamp in the last 4 bytes on the page. The page-header and page-ending time stamps are synchronized after each write, so they should be identical when the page is read from disk. Each read compares the time stamps as a test for data consistency. If the test fails, an error is returned to the user thread, indicating either that the disk page was not fully written to disk or that the page has been partially overwritten on disk or in shared memory. For a description of the content of a dbspace page, refer to dbspace structure and storage in the chapter on disk structures and storage in the IBM Informix: Administrator's Reference.