Oracle8 performance problem

When I query v$waitstat, the following appears:

  CLASS COUNT TIME

• ---------- ---------- data block 7380 35092 sort block 0 0 save undo block 0 0 segment header 226 20716 save undo header 0 0 free list 0 0 extent map 0 0 bitmap block 0 0 bitmap index block 0 0 unused 0 0 system undo header 0 0 system undo block 0 0 undo header 1701 144415 undo block 188 15584

         The above statistics shows a lot of waits in data block,  segment header, undo header and undo block. What do they mean? How can  I reduce the waits?

Regards,
Andrew

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