Rescue data in the worst situation (1)
To guarantee the safety of our data, we need to prepare a good backup/restore plan as well as Disaster Recovery solutions. However, for some reasons, many database systems are not maintained very well, and may encounter some fatal issues, e.g. Control files and Online REDO log fils are lost. In such situation, we need use some un-normal methods, such as hidden parameters, BBED and even Dul, to rescue the data. Now, my question is that, what is the worst situation having hope to rescue data. Theoretically, the data is comprised 2 important parts, data definition (also known as meta data) and data records. The data records are stored in the user data files, and the meta data is stored in system data files. Let's say, if there are only system files and key user data files (not all of data files) are un-corrupted, is it possible to rescue the data? Of course, we are not discussing using Dul to rescue the data.