Specifies the approximate number of data blocks containing data logically related to blocks with similar block numbers. Users can improve database access by organizing data in a way that it is logically (in data blocks) and physically (in the hard disk) as adjacent as possible. With ADJACENCY specified, a MUPIP INTEG operation reports adjacency of logically related data.
![[Note]](images/note.jpg) | |
The complexity of contemporary disk controllers and the native file system may render this report superfluous. But when it is meaningful, ADJACENCY is a tool for improving performance by measuring the adjacency of logically related data and increasing it using MUPIP REORG. |
The format of the ADJACENCY qualifier is:
-AD[JACENCY]=integer
By default, ADJACENCY is 10 for a MUPIP INTEG operation.
Database architects must ensure that ADJACENCY is close to the number of blocks that can physically reside on one hard disk's cylinder. One could also choose two or three cylinders, with the thought that short seeks are fast.
While native file system defragmentation improves physical adjacency of data, MUPIP REORG improves logical adjacency of data.