Indexing and Physical DB design

Question

Assume unspanned blocking and 100 B block file consist of records of 20,50,35,70,40,20 bytes. What % of space will be wasted..?

Answer 1

Unspanned means entire record should be in one block

1st block will contain only 20 and 50. we will have to place 35 in 2nd block becoz 1st block have remaining space = 100-20-50 = 30

2nd block will have only 35 becoz we cant accomodate 70 Byte block, since remaining space in 2nd block = 100-35 = 65

3rd block will have only 70 becoz we cant accomodate 40 Byte block, since remaining space in 3rd block = 100-70 = 30

4th block will have both 40 and 20 and remaining space will be 100-40-20 = 40

Total space wasted = 30 + 65 + 30 + 40 = 165

total block size = 4*100 = 400

so % space wasted = $\frac{165}{400}$ * 100 = 41.25%

Comments

thnx

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there is 65 byte space remaining in second block.. then why we can't put 20 & 40 byte in block 2.. in this way we don't need 4th block..