Multilevel Indexing Scheme

Consider the indexing scheme where the address of the block is consider in the index for each record, for a little file, this index would be little and can be processed efficiently in the main memory. Though, for a large file the size of index can also be very big. In such a case, one can make a hierarchy of indexes with the lowest level index pointing to the records, whereas the higher level indexes point to the indexes on indexes.

The following points about the multi-level indexes given below:

• The lowest level index points to every record in the file; therefore is costly in terms of space.
• Insertion, updating, and deletion of records need changes to the multiple index files as well as the data file. Therefore, maintenance of the multi-level indexes is also expensive.

After discussing so much about the indexes let us now turn our attention to how an index can be executed in a database. The indexes are executed through B Trees. The following section defines the index execution in more detail.