Distributed Database Management Systems: Lecture 13. The main topics covered in this chapter include: interests of the local and head offices mar result following vertical partitions of this table: EMP1(eId, eName, eDept); EMP2(eId, eQual, eSal); degree of fragmentation; correctness rules for fragmentation;...
Distributed Database Management Systems Lecture 13 How Interests of the local and head offices mar result following vertical partitions of this table: EMP1(eId, eName, eDept) EMP2(eId, eQual, eSal) Virtual University of Pakistan 1- Vertical; Different subsets of attributes are stored at different places, like, Table EMP(eId, eName, eDept, eQual, eSal) Virtual University of Pakistan Interests of the local and head offices may result following vertical partitions of this table: EMP1(eId, eName, eDept) EMP2(eId, eQual, eSal) Virtual University of Pakistan CLIENT (cAC#, cName, cAdr, cBal) table is placed in different databases based on their location, like from Lahore, Pindi, Karachi, Peshawar, Quetta Virtual University of Pakistan 3- Degree of Fragmentation Between no to the extreme level that could be to the individual tuple or column level; a compromised decision Virtual University of Pakistan 4- Correctness Rules for Fragmentation Virtual University of Pakistan • Completeness: each of the data item (a tuple or a attribute) that can be in R can also be in one or more Ri ∀ x ∈ R, ∃ Ri such that x ∈ Ri Resembles Lossless decomposition property in Normalization Virtual University of Pakistan • Reconstruction: it should be possible to define a relational operator such that the original relation can be reconstructed R = g(R1, R2, …, Rn) Reconstruction ensures that the dependencies of the original relation are preserved in fragmentation Virtual University of Pakistan • Disjoint ness: if data item x is in Rj, it is not in any other fragment ∀ x ∈ Ri, ∃ Rj such that x ∈ Rj, i ≠ j Virtual University of Pakistan 10 • Allocation Strategy: Partitioned, fully or partially replicated; depends mainly on requirements Virtual University of Pakistan 11 Horizontal Fragmentation Virtual University of Pakistan 12 • Partitions a table along its tuples • is performed based on some Predicate/ Condition Virtual University of Pakistan 13 Primary Horizontal Fragmentation(PHF) Virtual University of Pakistan 14 Information Requirements Virtual University of Pakistan 15 Database Information: We may need to consult the conceptual DB design RDM being Semantically not that rich Apart from tables, we need relationships, cardinality and the owner and member tables Virtual University of Pakistan 16 PAY EMP title, sal owner = PAY member = EMP eNo, Name, title ASIGN Virtual University of Pakistan jNo, jName, budget, loc eNo, jNo, resp, dur 17 PROJ Application Requirement Virtual University of Pakistan 18 ... Virtual University of Pakistan 13 Primary Horizontal Fragmentation(PHF) Virtual University of Pakistan 14 Information Requirements Virtual University of Pakistan 15 Database Information: We may... eSal) Virtual University of Pakistan CLIENT (cAC#, cName, cAdr, cBal) table is placed in different databases based on their location, like from Lahore, Pindi, Karachi, Peshawar, Quetta Virtual University