Version 8 introduced Type 2 indexes as a new standard index type, replacing the V7 Type 1 indexes.

Both indexes currently coexist, however, Type 1 indexes will be de-supported in the future. The type 2 index is replacement for the old Type 1 index, which has suffered from:

• concurrency issues during inserts and next key locks

•  performance issues due to physically removing a key from a leaf page during update or delete
  

Some benefits of Type 2 indexes:

• no more physical action after delete or update action until final commit

• next-key locking is reduced to a minimum, dramatically improving concurrency

• online index reorganization supported

• can be created on columns whose length is greater than 255 bytes