##### GATE 1993: How to solve ? I repeatedly get confused among

GATE 1993: How to solve ?

I repeatedly get confused among the terminologies. Kindly someone explain the difference between data, key field, pointer and satellite information ?

Arul 6 Jan 2015 05:41 am

data area:

I think, finding the number of blocks needed to store records should be easy.

(16K records * 64B each)/512B = 2K blocks

index area:

since, Data records are stored in blocks, For every Block of data records, people wanted to take out only a particular index (say, a starting index) & a pointer, so that they can do a binary search on it.

We need keyfield + block address for every block of data records. we have 2K blocks * (2+14) B of key & pointers = 32KB. It can be stored in 32KB/512 = 64 blocks.

For this 64 blocks, we can again make an index file with 64 keyfield+block address for every block.

So, totally 64 + 1 = 65 index area blocks are needed & we have 2 levels in the index tree.

Thanks for the question anyway.

TarGate 6 Jan 2015 08:00 pm

Thanks :) So ISAM is basically nothing but a B+ Tree, right ?

Arul 6 Jan 2015 08:07 pm

well, I would say, it is a tree, but not dynamic as like B+ tree.

TarGate 7 Jan 2015 09:09 pm

Correct. Researched a bit. Got to know ISAM has to maintain overflow blocks and has issues with insertions and updations. Where as for B Tree/B+ Tree, the algorithms are dynamic in nature and accommodate insertions and deletions perfectly :)