Specify an offset
When you allocate a chunk of disk space to the database server, specify an offset.
Specify an offset for one of the following two purposes:
- To prevent the database server from overwriting the partition information
- To define multiple chunks on a partition, disk device, or cooked file
The maximum value for the offset is 4 terabytes.
Many computer systems and some disk-drive manufacturers keep information for a physical disk drive on the drive itself. This information is sometimes called a volume table of contents (VTOC) or disk label. The VTOC is commonly stored on the first track of the drive. A table of alternative sectors and bad-sector mappings (also called a revectoring table) might also be stored on the first track.
If you plan to allocate partitions at the start of a
disk, you might be required to use offsets to prevent the database
server from overwriting critical information required by the operating
system. For the exact offset required, see your disk-drive manuals.
Important: If you are running two or more instances of the database
server, be extremely careful not to define chunks that overlap. Overlapping
chunks can cause the database server to overwrite data in one chunk
with unrelated data from an overlapping chunk. This overwrite effectively
deletes overlapping data.