Recover lost data from VxFS and UFS file system volumes after Object Location Table corruption, Boot errors, operating system damage from SCSI, EIDE and IDE hard drives

In a SCO OpenServer based computer, VTOC (Volume Table of Contents) is a metadata structure, which provides the way to find out data sets that are located on specific hard drive volume.

• The data set is a file having record organization. Data sets are generally stored on DASD (Direct Access Storage Device) or magnetic tape.

The VTOC is stored in the first 64K memory tracks of the hard drive volume. It indexes the names of every data set on volume as well as the size, permissions and location. Furthermore, it has an entry for each area of adjacent free space on disk volume.

Third record on first track of first cylinder of a DASD volume is called volume label and contains a pointer to the memory location of VTOC. The VTOC is attached to hard drive when it is first initialized using Device Support Facilities tool, ICKDSF.

To find out and access data sets, an application would interrogate SCO OpenServer catalog and locate the volume where original data sets are stored. Having found the appropriate volume, VTOC is searched to locate where the data sets are stored on hard drive.

VTOC includes records, called BSCB (Data Set Control Blocks). There are generally seven types of DSCBs are used by VTOC.

For SCO OpenServer to access hard drive volumes, it is essential to have a properly working VTOC. If it gets corrupted due to any reason such as virus attack, improper use of fsck, unexpected system shutdown and the similar reasons, operating system can not locate the data volumes and thus can not access your data.