DBMS Unit 4 & 5 Short Notes

4.5. What’s serializability? How it’s tested? AKTU 2016- 17, Marks 02 Ans. Serializability is the classical concurrency scheme which ensures that a schedule for executing concurrent sale serially in same order. Serializability is tested by constructing priority graph. . Define schedule. Ans. A schedule is a list of operations( conduct) ordered by time, performed by a set of deals that are executed together in the system. . What do you mean by periodical schedule? Ans. periodical schedule is a schedule in which deals in the schedule are defined to execute one after the other. . Define replication in distributed database. AKTU 2017- 18, Marks 02 Ans. Replication is a fashion used in distributed databases to store multiple clones of a data table at different spots. . Define data atomicity. Ans. Data atomicity is one of the sale parcels which specify that either all operations of the sale are reflected duly in the database or not. . Define slinging rollback and eyeless writes. Ans. Slinging rollback is a situation in which failure of single sale leads to a series of sale rollbacks. Blind writes are those write operations which are performed without performing the read operation. . Define priority graph. Ans. A priority graph is a directed graph G = ( N, E) where N = { T1, T2,., Tn} is a set of bumps and E = { e1, e2. en} is a set of directed edges. . Give types of failures. Ans. Types of failures sale failure ii. System crash iii. Fragment failure . Give the idea behind shadow paging fashion. Ans. The crucial idea behind shadow paging fashion is to maintain following two runner tables during the life of sale Current runner table ii. Shadow runner table . Give graces and faults of shadow paging. Ans. graces of shadow paging i. The outflow of log record affair is excluded. ii. Recovery from crashes is significantly briskly. faults Commit above ii. Data fragmentation iii. Garbage collection . What’s multimedia database? Ans. Multimedia database provides features that allow druggies to store and query different types of multimedia information, which includes images( filmland or delineations), videotape clips( pictures, news rolls, home videotape), audio clips( songs, phone dispatches, speeches) and documents books, papers). . Why is it desirable to have concurrent prosecution of multiple deals? Ans. It’s desirable to have concurrent prosecution of multiple sale To increase system outturn. ii. To reduce average response time. . What do you mean by conflict serializable schedule? Ans. A schedule is called conflict serializable if it can be converted into a periodical schedule by switchingnon-conflicting operation. . Define concurrency control. Ans. Concurrency Control( CC) is a process to insure that data is streamlined rightly and meetly when multiple deals are coincidently executed in DBMS. 5UNIT . Why is concurrency control demanded? Ans. Concurrency control is demanded so that the data can be streamlined rightly when multiple deals are executed coincidently. . Write down the main orders of concurrency control. Ans. orders of concurrency control are Auspicious ii. Pessimistic iii. Semi-optimistic . What do you mean by auspicious concurrency control? Ans. Auspicious concurrency control countries means deals fails when they commit with conflicts. It’s useful where we do not anticipate conflicts but if it occurs than the committing sale is rollbacked and can be renewed. . Define cinches. Ans. A cinch is a variable associated with each data item that indicates whether read or write operation is applied. . Define the modes of cinch. Ans. Data particulars can be locked in two modes 1. Exclusive( X) mode If a sale Ti has attained an exclusive mode cinch on item Q, also Ti can read as well as write Q data item. 2. Shared( S) mode If a sale Ti has attained a participated mode cinch on item Q, also Ti can only read the data item Q but Ti can not write the data itemQ. . Give graces and faults of two- phase locking. Ans. graces of two phase locking i. It maintains database thickness. ii. It increases concurrency over static locking as cinches are held for shorter period. faults of two- phase locking impasse ii. Cascade aborts rollback . Define cinch comity. Ans. Cinch comity determines whether cinches can be acquired on a data item by multiple deals at the same time. . Define upgrade and downgrade in locking protocol. Ans. Upgrade Upgrade is the cinch conversion from participated to exclusive mode. It takes place only in growing phase. Downgrade Downgrade is the cinch conversion from exclusive to participated mode. It can take place only in shrinking phase. . Define the term intention cinch. Ans. Intention cinch is a type of cinch mode used in multiple granularity locking in which a sale intends to explicitly lock a lower position of the tree. To give a advanced degree of concurrency, intention mode is associated with participated mode and exclusive mode. . What are the risks of cinch grounded protocol? Ans. risks of cinch grounded protocols are impasse can do. ii. Starvation is also possible if concurrency control director is poorly designed. . Define exclusive cinch. Ans. Exclusive cinch is a cinch which provides only one stoner to read a data item at a particular time. . Define timestamp. Ans. A timestamp is a unique identifier created by the DBMS to identify a sale. This timestamp is used in timestamp grounded concurrency control ways. . Define multiversion scheme. Ans. Multiversion concurrency control is a scheme in which each write( Q) operation creates a new interpretation of Q. When a sale issues a read( Q) operation, the concurrency control director selects one of the interpretation of Q to be read that ensures serializability. . Define Thomas ’ write rule. Ans. Thomas ’ write rule is the revision to the introductory timestamp ordering, in which the rules for write operations are slightly different from those of introductory timestamp ordering. It doesn’t apply conflict serializability.

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