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Optimistic concurrency control sets few locks on the data in the database, lowering the isolation level that you use in an application. This allows more applications to run concurrently and potentially increases the throughput of the applications. This strategy attempts to obtain locks on the required resources only when the transaction completes.Pessimistic concurrency control implements a higher isolation level by placing locks on the database at the beginning of a transaction. In other words, pessimistic locking assumes there will be a collision in the database and takes precautions to prevent these collisions. A pessimistic locking strategy protects the integrity of the database by guaranteeing, from the beginning of the transaction, that no conflicting transaction can run concurrently.The optimistic concurrency control strategy always allows a transaction to start but cannot guarantee that it will complete. The pessimistic locking strategy cannot guarantee that a transaction will be able to start, but it guarantees that, once started, any transaction can complete.A data warehouse has many fetches, or SELECTs, and few DMLs, or UPDATEs, INSERTs, and DELETEs. An online transaction processing (OLTP) application usually has many DMLs and few SELECTs. Remember that rows selected from a partially complete transaction may not be consistent.Discuss the following points:Identify one benefit and one drawback of each concurrency control strategy in an OLTP application. Explain.Identify one benefit and one drawback of each concurrency control strategy in a data warehouse. Explain.Suggest a scenario for a hypothetical OLTP business system where optimistic concurrency control is most appropriate and another scenario where pessimistic concurrency control is most appropriate.How would the type of user, such as a computer program, an internal business user, or a customer on the web, affect your choices?
Code an Oracle Database trigger to enforce the constraint that an employee can never change his or her department.
Identify two possibly mispriced bond issues, one overpriced and one underpriced. and graph the bond yield to maturity (YTM) on the y-axis of an XY-scatter plot, with the bond to maturity in years on the x-axis.
Database Questions: What do you mean by data base scheme? What do you mean by cardinality ratio? What do you mean by degree of relation?
The DBA denormalized some of the data in Premiere Products database to enhance performance, and one of the resulting tables is following.
Design a Database schema
The DBA denormalized some of the data in the Premiere Products database to improve performance. Which field or fields cause the table to no longer be in third normal form? In which normal form is the denormalized table?
Database designers stated following dimension of "miniworld"- to be represented in Company Supplier-Part database: company is organized into departments. Each department has unique name, unique number.
Developers have noticed that EMP table doesn't have an assigned primary key. EMP_ID column has been selected to be the primary key.
The relations given below keep track of airline flight information:Flights(flno: integer, from: string, to: string, distance:integer, departs: time, arrives: time, price: real)Aircraft(aid: integer, aflame: string, cruisingrange: integer)
Why are these so significant yet so frequently ignored by developers? Write the long term problems when these constraints are not implemented? "
What are the functional dependencies among the data represented in this first normal form relation?
What are the main activities that the business undertakes and where in the business are the crucial decisions made?
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