Distributed Database Management Systems: Lecture 25. The main topics covered in this chapter include: derived horizontal fragmentation; fragmenting/partitioning a table based on the constraints defined on another table; linked with each other through Owner-Member relation;...
Distributed Database Management Systems Lecture 25 Distributed Database Management Systems Virtual University of Pakistan In Previous Lectures: time 1:40230 • Reasons for Fragmentation – Maximizes local access – Reduces table size, etc • PHF using the SQL Server on same machine In Previous Lectures 2:00 • DDBS design is a team effort • Involves – Domain Experts – DDBS Experts – Network Experts In Previous Lectures • Implemented PHF in a Banking Environment (around 3: 40) • DDBS layer is superimposed on the client sites (4:00) • Actual Data resides with the local sites (4:35) Today’s Lecture Derived Horizontal Fragmentation Derived Horizontal Fragmentation • Fragmenting/ Partitioning a table based on the constraints defined on another table • Both tables are linked with each other through Owner-Member relation Time: 5:36 Owner TABLE1 a, b, c, d Link TABLE2 p, q, r, s, a Member Scenario (around 7:25) Owner TITLE titleId, titleName, sal Link EMP empId, empName, empAdres, titleId Member Why DHF Here (8: 50) • Employee and salary record is split in two tables due to Normalization • Storing all data in EMP table introduces Transitive Dependency • That causes Anomalies • On next slide is asks the schedule for Distributor A couple of more nexts and then • After this we run the snapshot agent, that creates a snapshot, you can verify this from snapshot agent history, or you can go to subscriber database and have a look, like this • We delete a record from our publication and we see that it is expressed in • This will be automatically be transferred to Subscription • If this activity could not be performed on subscriber, then the replication monitor will generate an error You have to trap it and tune your application Merge Replication • From replication, start a new publication, a few nexts, and once again our old familiar screen • After a few nexts, the merge publication will be created • • • • Now you execute the snapshot agent of this replication It will create the snapshot, then you subscribe a database We find the original data in the subscriber After this if we make any change on either side, it will be reflected on the other side • In case of merge replication, we have to be careful about the constraints, like Primary Key, or other constraints .. .Distributed Database Management Systems Virtual University of Pakistan In Previous Lectures: time 1:40230 • Reasons for Fragmentation – Maximizes... SQL Server on same machine In Previous Lectures 2:00 • DDBS design is a team effort • Involves – Domain Experts – DDBS Experts – Network Experts In Previous Lectures • Implemented PHF in a Banking... char (25) , empAdres char (30), titleId char(3) foreign key references TITLE1(titleID) not NULL) Defining all three EMP tables:21:20 • create table EMP1 (empId char(5) primary key, empName char (25) ,