Interview Questions.

Q1. Since Indices Speed Query Processing, Why Might They Not Be Kept On Several Search Keys?

Reasons for no longer retaining several search indices include:

Every index requires extra CPU time and disk I/O overhead at some stage in inserts and deletions.

Indices on non-number one keys would possibly need to be modified on updates, even though an index at the primary key may not (this is because updates generally do no longer regulate the number one key attributes).

Each more index requires additional garage space.

For queries which involve conditions on several search keys, performance may not be horrific even though only a few of the keys have indices on them. Therefore database performance is advanced less by way of including indices when many indices already exist

Q2. Explain The Distinction Between Condition-defined And User-defined Constraints. Which Of These Constraints Can The System Check Automatically?

In a generalization–specialization hierarchy, it must be viable to decide which entities are individuals of which decrease stage entity sets. In a situation defined layout constraint, club within the lower level entity-units is evaluated on the idea of whether or not or not an entity satisfies an specific situation or predicate.User-defined decrease-level entity units are not restrained by using a club situation; as an alternative, entities are assigned to a given entity set by way of the database consumer.

Condition-described constraints by myself can be routinely handled by means of the gadget. Whenever any tuple is inserted into the database, its membership in the diverse lower degree entity-sets can be robotically determined by using evaluating the respective membership predicates. Similarly whilst a tuple is up to date, its membership within the various entity units may be re-evaluated routinely.

Q3. List Five Responsibilities Of A Database Management System?

A widespread reason database supervisor (DBM) has five obligations:

interplay with the document manager.

Integrity enforcement.

Protection enforcement.

Backup and recovery.

Concurrency manipulate.

Q4. Discuss The Relative Advantages Of Centralized And Distributed Databases?

A distributed database lets in a consumer handy and trparent get right of entry to to information which is not saved on the website online, at the same time as allowing each website manipulate over its personal nearby records. A allotted database may be made greater dependable than a centralized gadget because if one site fails, the database can preserve functioning, but if the centralized machine fails, the database can no longer hold with its everyday operation. Also, a disbursed database lets in parallel execution of queries and likely splitting one question into many elements to growth throughput.

A centralized machine is less difficult to design and put in force. A centralized device is cheaper to operate because messages do no longer must be sent.

Q5. What Are The Factors That Can Work Against Linear Scale Up In A Traction Processing System?Which Of The Factors Are Likely To Be The Most Important In Each Of The Following Architectures: Shared Memor

Increasing competition for shared assets prevents linear scale-up with increasing parallelism. In a shared reminiscence device, competition for reminiscence (which suggests bus rivalry) will result in falling scale-up with increasing parallelism. In a shared disk gadget, it's miles rivalry for disk and bus access which impacts scale-up. In a shared-nothing machine, inter-manner verbal exchange overheads can be the main impeding element. Since there may be no shared reminiscence, obtaining locks, and other activities requiring message passing between methods will take greater time with expanded parallelism.

Q6. When Is It Preferable To Use A Dense Index Rather Than A Sparse Index?

It is ideal to apply a dense index in place of a sparse index while the file isn't sorted on the listed field (including whilst the index is a secondary index) or when the index document is small in comparison to the size of reminiscence.

Q7. Explain Why 4nf Is A Normal Form More Desirable Than Bcnf?

4NF is more perfect than BCNF as it reduces the repetition of data. If we consider a BCNF schema not in 4NF (see Exercise 7.28), we look at that decomposition into 4NF does no longer lose data furnished that a loss less join decomposition is used, yet redundancy is reduced.

Q8. Explain Why A Physical Oid Must Contain More Information Than A Pointer To A Physical Storage Location?

A physical OID needs to have a unique identifier further to a pointer to a physical storage location. This is needed to save you dereferences of dangling recommendations.

Q9. If Physical Oids Are Used, An Object Can Be Relocated By Keeping A Forwarding Pointer To Its New Location. In Case An Object Gets Forwarded Multiple Times, What Would Be The Effect On Retrieval Spee

If an object receives forwarded multiple times, the retrieval pace will lower because having access to it's going to require having access to the collection of locations from which the item has been successively forwarded to the present day region. Multiple accesses can be averted by way of continually preserving inside the oldest region the modern cope with of the object. This can be executed by way of checking while forwarding whether or not this item has already been forwarded and in that case updating the forwarding cope with at the oldest region. Thus, atmost  accesses may be required.

Q10. We Described The Use Of Views To Simplify Access To The Database By Users Who Need To See Only Part Of The Database. The Use Of Views As A Security Mechanism. Do These Two Purposes For Views Ever Con

Usually, a properly-designed view and security mechanism can keep away from conflicts among ease of get admission to and protection. However, as the subsequent instance suggests, the 2 functions do battle in case the mechanisms aren't designed cautiously.

Suppose we've a database of employee facts and a consumer whose view includes worker data for employees incomes less than $10,zero@If this consumer inserts worker Jones, whose earnings is $9,000, however by chance enters $ninety,000, several existing database structures will be given this update as a valid replace through a view. However, the consumer can be denied get right of entry to to delete this inaccurate tuple by way of the security mechanism.

Q11. In Multiple-granularity Locking, What Is The Difference Between Implicit And Explicit Locking?

When a traction explicitly locks a node in shared or extraordinary mode, it implicitly locks all the descendents of that node within the identical mode. The traction want no longer explicitly lock the descendent nodes. There is not any difference in the functionalities of those locks, the simplest distinction is within the manner they're received, and their presence examined.

Q12. List The Acid Properties. Explain The Usefulness Of Each?

The ACID houses, and the need for each of them are:-

Consistency: Execution of a traction in isolation (that is, and not using a other traction executing concurrently) preserves the consistency of the database. This is typically the responsibility of the software programmer who codes the tractions.

Atomicity: Either all operations of the traction are reflected nicely in the database, or none are. Clearly loss of atomicity will result in inconsistency within the database.

Isolation: When a couple of tractions execute concurrently, it must be the case that, for each pair of tractions Ti and Tj , it appears to Ti that either Tj completed execution earlier than Ti started, or Tj commenced execution after Ti completed. Thus, each traction is blind to other tractions executing concurrently with it. The person view of a traction system requires the isolation property, and the belongings that concurrent schedules take the machine from one steady state to some other. These necessities are glad with the aid of ensuring that best serializable schedules of in my view consistency preserving tractions are allowed.

Durability: After a traction completes efficiently, the modifications it has made to the database persist, although there are device screw ups.

Q13. Consider A Two-dimensional Integer Array Of Size N ×m That Is To Be Used In Your Favorite Programming Language. Using The Array As An Example, Illustrate The Difference?

Betw

Let tgrid be a two-dimensional integer array of size n × m.

The bodily degree could really be m × n (likely consecutive) storage locations of anything length is specific with the aid of the implementation (e.G., 32 bits each).

The conceptual degree is a grid of boxes, every possibly containing an integer, which is n packing containers high via m containers extensive.

There are 2m×n possible perspectives. For example, a view might be the whole array, or particular row of the array, or all n rows however handiest columns 1 through i.

Consider the following Pascal declarations: type tgrid = array[1..N, 1..M] of integer; var vgrid1, vgrid2 : tgrid Then tgrid is a schema, while the price of variables vgrid1 and vgrid2 are times.

To illustrate in addition, don't forget the schema array[1..2, 1..2] of integer. Two times of this scheme are:

Q14. Explain The Distinction Between Total And Partial Constraints?

In a total design constraint, each better-degree entity should belong to a decrease-degree entity set. The identical need now not be actual in a partial design constraint. For instance, a few personnel may belong to no work-group.

Q15. What Are Two Advantages Of Encrypting Data Stored In The Database?

Encrypted statistics permits authorized users to access facts without worrying approximately different users or the gadget administrator gaining any records.

Encryption of records may additionally simplify or maybe make stronger other authorization mechanisms. For instance, distribution of the cryptographic key amongst most effective relied on users is each, a easy way to control study get entry to, and an brought layer of safety above that offered via views.

Q16. Under What Conditions Is It Less Expensive To Avoid Deadlock Than To Allow Deadlocks To Occur And Then To Detect Them?

Deadlock avoidance is superior if the effects of abort are severe (as in interactive tractions), and if there's excessive contention and a resulting excessive probability of impasse.

Q17. List Two Reasons Why We May Choose To Define A View?

Security situations may require that the entire logical database be now not seen to all customers.

We may desire to create a customized collection of members of the family that is better matched to a positive user’s instinct than is the real logical version.

Q18. Explain The Distinction Between Closed And Open Hashing. Discuss The Relative Merits Of Each Technique In Database Applications?

Open hashing may additionally place keys with the same hash feature cost in one of a kind buckets. Closed hashing constantly places such keys collectively in the same bucket. Thus in this example, distinct buckets can be of different sizes, although the implementation can be by using linking together constant size buckets using overflow chains. Deletion is hard with open hashing as all of the buckets may additionally need to inspected before we can ascertain that a key value has been deleted, whereas in closed hashing handiest that bucket whose address is received through hashing the important thing value want be inspected. Deletions are more commonplace in databases and hence closed hashing is greater suitable for them. For a small, static set of records lookups can be greater efficient the use of open hashing. The symbol desk of a compiler would be an awesome instance.

Q19. Explain The Distinction Between The Terms Serial Schedule And Serializable Schedule.

A time table wherein all the commands belonging to 1 single traction seem collectively is known as a serial agenda. A serializable schedule has a weaker limit that it have to be equal to a few serial schedule. There are  definitions of time table equivalence – war equivalence and examine equivalence. Both of these are defined within the bankruptcy.

Q20. Consider A Network Based On Dial-up Phone Lines, Where Sites Communicate Periodically, Such As Every Night. Such Networks Are Often Configured With A Server Site And Multiple Client Sites. The Clien

With the crucial server, every web page does no longer have to recall which website online to touch while a particular information item is to be requested. The vital server on my own wishes to keep in mind this, so information objects may be moved round effortlessly, depending on which sites get right of entry to which items most often.Other house-preserving responsibilities are also centralized in preference to allotted, making the machine simpler to develop and hold. Of path there may be the downside of a complete shutdown in case the server becomes unavailable. Even if it's far strolling, it could become a bottleneck because every request needs to be routed through it.

Q21. List The Physical Storage Media Available On The Computers You Use Routinely. Give The Speed With Which Data Can Be Accessed On Each Medium?

Your wer might be primarily based at the computer systems and garage media which you use. Typical examples would be difficult disk, floppy disks and CD-ROM drives.

Q22. Explain How Dangling Tuples May Arise. Explain Problems That They May Cause?

Dangling tuples can rise up when one tuple is inserted into a decomposed relation but no corresponding tuple is inserted into the other members of the family in the decomposition. They can cause incorrect values to be returned by means of queries which form the be a part of of a decomposed relation for the reason that dangling tuple may not be protected. Dangling tuples can be prevented by means of the specification of referential integrity constraints.

Q23. Consider The Validation-based totally Concurrency-control. Show That By Choosing Validation(ti), Rather Than Start(ti), As The Time Stamp Of Traction Ti, We Can Expect Better Response Time Provided That Confl

In the concurrency manage scheme deciding on Start(Ti) as the time stamp of Ti gives a subset of the schedules allowed by using choosing Validation(Ti) as the time stamp. Using Start(Ti) me that whoever commenced first need to finish first. Clearly tractions ought to enter the validation section in the identical order in which they started out executing, but this is overly restrictive. Since deciding on Validation(Ti) reasons fewer non conflicting tractions to restart, it gives the higher response instances.

Q24. Explain The Phantom Phenomenon. Why May This Phenomenon Lead To An Incorrect Concurrent Execution Despite The Use Of The Two-section Locking Protocol?

The phantom phenomenon arises when, due to an insertion or deletion, two tractions logically battle in spite of no longer locking any information objects in not unusual. The insertion case is defined within the ebook. Deletion also can lead to this phenomenon. Suppose Ti deletes a tuple from a relation while Tj sc the relation. If Ti deletes the tuple and then Tj reads the relation, Ti must be serialized before Tj . Yet there may be no tuple that each Ti and Tj warfare on.

An interpretation of 2PL as simply locking the accessed tuples in a relation is wrong. There is likewise an index or a relation data that has facts approximately the tuples within the relation. This data is examine by way of any traction that sc the relation, and modified by using tractions that update, or insert into, or delete from the relation. Hence locking have to additionally be finished at the index or relation data, and this may keep away from the phantom phenomenon.

Q25. Construct An E-r Diagram For A Car-coverage Company Whose Customers Own One Or More Cars Each. Each Car Has Associated With It Zero To Any Number Of Recorded Accidents?

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Q26. Give An Example Where Lazy Replication Can Lead To An Inconsistent Database State Even When Updates Get An Exclusive Lock On The Primary (master) Copy?

Consider the stability in an account, replicated at N web sites. Let the modern-day stability be $a hundred – steady throughout all websites. Consider two tractions T1 and T2 every depositing $10 inside the account. Thus the balance would be $one hundred twenty after each these tractions are completed. Let the tractions execute in series: T1 first and then T@Suppose the reproduction of the balance at one of the web sites, say s, isn't constant – due to lazy replication method – with the primary reproduction after traction T1 is executed and allow traction T2 examine this reproduction of the balance. One can see that the balance at the primary web page might be $110 at the end.

Q27. How Does The Concept Of An Object In The Object-oriented Model Differ From The Concept Of An Entity In The Entity-relationship Model?

An entity is certainly a group of variables or facts objects. An object is an encapsulation of statistics as well as the strategies (code) to perform on the records. The records members of an item are at once visible only to its strategies. The outdoor world can gain get right of entry to to the item’s facts most effective by means of passing pre-described messages to it, and those messages are applied via the methods.

Q28. Raid Systems Typically Allow You To Replace Failed Disks Without Stopping Access To The System. Thus, The Data In The Failed Disk Must Be Rebuilt And Written To The Replacement Disk While The System

RAID stage 1 (mirroring) is the one which allows rebuilding of a failed disk with minimal interference with the on-going disk accesses. This is because rebuilding in this example involves copying information from just the failed disk’s reflect. In the other RAID ranges, rebuilding entails reading the whole contents of all the other disks.

Q29. Consider A File System Such As The One On Your Favorite Operating System.

What Are The Steps Involved In Creation And Deletion Of Files, And In Writing Data To A File?

Provide an explanation for H

There are numerous steps inside the introduction of a record. A storage area is assigned to the record within the record machine, a unique i-number is given to the document and an i-node entry is inserted into the i-listing. Deletion of file includes exactly contrary steps.

For the file machine user in UNIX, durability is essential for obvious motives, but atomicity isn't applicable typically because the document gadget doesn’t help tractions. To the report gadget implementor even though, a few of the internal record machine actions want to have traction semantics. All the stairs involved in introduction/deletion of the file have to be atomic, otherwise there will be unreferenceable files or unusable regions inside the file device.

Q30. During Its Execution, A Traction Passes Through Several States, Until It Finally Commits Or Aborts. List All Possible Sequences Of States Through Which A Traction May Pass. Explain Why Each State Tri

The possible sequences of states are:-

active→partially dedicated→dedicated. This is the ordinary series a successful traction will follow. After executing all its statements it enters the in part committed nation. After sufficient recovery statistics has been written to disk, the traction sooner or later enters the dedicated state.

Active → partially devoted → aborted. After executing the ultimate assertion of the traction, it enters the partly devoted country. But earlier than sufficient recuperation records is written to disk, a hardware failure might also arise destroying the reminiscence contents. In this example the modifications which it made to the database are undone, and the traction enters the aborted country.

Lively → failed → aborted. After the traction begins, if it's miles located sooner or later that regular execution can not hold (either due to internal program mistakes or external mistakes), it enters the failed nation. It is then rolled back, after which it enters the aborted state.

Q31. Explain The Distinction Between A Type X And A Reference Type Ref(x). Under What Circumstances Would You Choose To Use A Reference Type?

If the type of an characteristic is x, then in every tuple of the desk, similar to that characteristic, there's an actual item of type x . If its kind is ref(x), then in each tuple, corresponding to that characteristic, there's a connection with a few item of type x. We choose a reference type for an attribute, if that attribute’s supposed motive is to refer to an independent item.

Q32. Explain The Notions Of Trparency And Autonomy. Why Are These Notions Desirable From A Human-factors Standpoint?

Autonomy is the quantity of control a single web page has over the neighborhood database. It is essential due to the fact users at that web site need brief and accurate access to nearby statistics gadgets. This is mainly authentic while one considers that nearby records can be most regularly accessed in a database. Trparency hides the allotted nature of the database. This is important due to the fact customers need to not be required to realize about region, replication, fragmentation or other implementation aspects of the database.

Q33. Justify The Following Statement: Concurrent Execution Of Tractions Is More Important When Data Must Be Fetched From (gradual) Disk Or When Tractions Are Long, And Is Less Important When Data Is In Memo

If a traction is very long or while it fetches statistics from a sluggish disk, it takes a long time to complete. In absence of concurrency, different tractions will must await longer period of time. Average response time will increase. Also while the traction is analyzing statistics from disk, CPU is idle. So resources are not properly applied. Hence concurrent execution turns into vital in this case. However, when the tractions are quick or the data is available in memory, those issues do no longer occur.

Q34. Write An Assertion For The Bank Database To Ensure That The Assets Value For The Perry Ridge Branch Is Equal To The Sum Of All The Amounts Lent By The Perry Ridge Branch?

The announcement-name is unfair. We have selected the call Perry. Note that since the statement applies handiest to the Perry ridge department we must limit attention to handiest the Perry ridge tuple of the branch relation as opposed to writing a constraint on the whole relation.

  Create assertion perry check  (now not exists (choose *  from department  in which department-call = ’Perryridge’ and  property = (choose sum (quantity)  from loan  in which branch-call = ’Perryridge’)))

Q35. How Does Data Encryption Affect Index Schemes? In Particular, How Might It Affect Schemes That Attempt To Store Data In Sorted Order?

Note that indices should operate on the encrypted data or a person may want to advantage get entry to to the index to interpret the facts.Otherwise, the index might ought to be constrained in order that handiest sure users should get entry to it. To hold the statistics in looked after order, the index scheme could have to decrypt the records at every level in a tree. Note that hash structures would now not be affected.

Q36. A Weak Entity Set Can Always Be Made Into A Strong Entity Set By Adding To Its Attributes The Primary Key Attributes Of Its Identifying Entity Set. Outline What Sort Of Redundancy Will Result If We

The number one key of a weak entity set may be inferred from its relationship with the robust entity set. If we add number one key attributes to the vulnerable entity set, they will be present in each the entity set and the relationship set and they should be the same. Hence there could be redundancy.

Q37. In Designing A Relational Database, Why Might We Choose A Non-bcnf Design?

BCNF isn't usually dependency keeping. Therefore, we may also want to choose another regular form (specially, 3NF) in an effort to make checking dependencies less difficult all through updates. This would avoid joins to check dependencies and growth gadget overall performance.

Q38. We Can Convert Any Weak Entity Set To A Strong Entity Set By Simply Adding Appropriate Attributes.Why, Then, Do We Have Weak Entity Sets?

We have vulnerable entities for numerous motives:

We need to keep away from the information duplication and consequent possible inconsistencies resulting from duplicating the important thing of the strong entity.

Weak entities replicate the logical structure of an entity being depending on another entity.

Weak entities may be deleted robotically while their sturdy entity is deleted.

Weak entities can be saved physically with their robust entities.

Q39. An E-r Diagram Can Be Viewed As A Graph.What Do The Following Mean In Terms Of The Structure Of An Enterprise Schema?

The Graph Is Disconnected.<

the Graph Is Acyclic.

If a pair of entity units are related by using a route in an E-R diagram, the entity units are associated, even though possibly in a roundabout way. A disconnected graph means that there are pairs of entity sets which are unrelated to each different. If we break up the graph into related components, we have, in effect, a separate database corresponding to each related issue.

As indicated in the wer to the previous component, a course within the graph between a pair of entity units indicates a (probably oblique) dating between the 2 entity units. If there's a cycle in the graph then each pair of entity sets at the cycle are related to each other in at least two awesome ways. If the E-R diagram is acyclic then there may be a unique direction between each pair of entity units and, as a result, a completely unique relationship between every pair of entity units.

Q40. Since Every Conflict-serializable Schedule Is View Serializable, Why Do We Emphasize Conflict Serializability Rather Than View Serializability?

Most of the concurrency control protocols (protocols for ensuring that handiest serializable schedules are generated) utilized in practice are based totally on war serializability—they truly allow simplest a subset of warfare serializable schedules. The fashionable shape of view serializability is very expensive to check, and best a very limited shape of it is used for concurrency control.

Q41. Consider A Grid File In Which We Wish To Avoid Overflow Buckets For Performance Reasons. In Cases Where An Overflow Bucket Would Be Needed, We Instead Reorganize The Grid File. Present An Algorithm

Let us remember a two-dimensional grid array. When a bucket overflows, we can break up the tiers similar to that row and column into , in each the linear scales. Thus the linear scales gets one additional entry each, and the bucket is cut up into 4 buckets. The stages ought to be cut up in any such manner as to make certain that the 4 resultant buckets have almost the identical variety of values.

There may be numerous different heuristics for identifying a way to reorganize the levels, and as a result the linear scales and grid array.

Q42. List Four Significant Differences Between A File-processing System And A Dbms?

Some essential differences between a database control machine and a document-processing gadget are:

Both structures contain a set of information and a hard and fast of applications which get entry to that statistics. A database control device coordinates both the physical and the logical get right of entry to to the statistics, while a record-processing system coordinates simplest the physical get right of entry to.

A database management system reduces the quantity of statistics duplication through making sure that a physical piece of data is available to all programs authorized to have get admission to to it,whereas statistics written with the aid of one software in a report-processing device may not be readable by way of every other application.

A database control gadget is designed to allow flexible get right of entry to to records (i.E., queries), whereas a report-processing machine is designed to permit predetermined get right of entry to to information (i.E., compiled applications).

A database management system is designed to coordinate more than one users gaining access to the same data on the equal time. A report-processing systemis normally designed to allow one or more applications to get admission to special records files on the identical time. In a record-processing machine, a record may be accessed by means of two applications simultaneously simplest if both applications have study-best get right of entry to to the report.

Q43. Explain The Distinction In Meaning Between Edges In A Dag Representing Inheritance And A Dag Representing Object Containment?

An edge from class A to magnificence B within the DAG representing inheritance me that an object of class B is likewise an object of class A. It has all the properties that objects of class A have, plus extra ones of its own. In specific, it inherits all the variables and methods of class A. It can of direction offer its personal implementations for the inherited strategies. And edge from class A to class B within the item containment DAG me that an object of sophistication A consists of an item of sophistication B. There need now not be any similarities within the houses of A and B. Neither B nor A inherit anything from the opposite. They function as impartial sorts, to the quantity that an item of class A can get right of entry to the variables of the B item contained in it handiest through the B object’s methods.

Q44. Why Are Certain Functional Dependencies Called Trivial Functional Dependencies?

Certain practical dependencies are known as trivial functional dependencies due to the fact they're happy with the aid of all relations.

Q45. Consider The Relational Database Of Figure four.

  Create view salinfo as  pick out supervisor-name, avg(profits)  from manages m, works w  wherein m.Worker-name = w.Worker-call  group through supervisor-name

Updates should no longer be allowed in this view due to the fact there may be no way to determine how to exchange the underlying statistics. For example, assume the request is “change the average profits of employees operating for Smith to $2 hundred”. Should everyone who works for Smith have their revenue changed to $two hundred? Or have to the primary (or more, if necessary) worker located who works for Smith have their profits adjusted so that the common is $two hundred?Neither method in reality makes feel.

Q46. Suppose There Are Two Relations R And S, Such That The Foreign Key B Of R References The Primary Key A Of S. Describe How The Trigger Mechanism Can Be Used To Implement The On Delete Cascade Option, W

We define triggers for every relation whose primary-secret is referred to by the overseas-key of a few different relation. The trigger could be activated on every occasion a tuple is deleted from the referred-to relation. The movement done through the cause could be to visit all the referring members of the family, and delete all of the tuples in them whose foreign-key attribute fee is similar to the number one-key attribute fee of the deleted tuple in the referred-to relation. These set of triggers will take care of the on delete cascade operation.

Q47. What Is The Difference Between A Primary Index And A Secondary Index?

The number one index is on the field which specifies the sequential order of the record. There can be handiest one primary index whilst there may be many secondary indices.

Q48. Use Of Multiple-granularity Locking May Require More Or Fewer Locks Than An Equivalent System With A Single Lock Granularity. Provide Examples Of Both Situations, And Compare The Relative Amount Of Co

If a traction needs to access a big a set of gadgets, a couple of granularity locking requires fewer locks, whereas if handiest one item needs to be accessed, the unmarried lock granularity machine lets in this with simply one lock. Because all of the desired records objects are locked and unlocked collectively in the a couple of granularity scheme, the locking overhead is low, but concurrency is also reduced.

Q49. What Is The Purpose Of Having Separate Categories For Index Authorization And Resource Authorization?

Index and useful resource authorization have to be unique classes to permit sure users to create members of the family (and the indices to function on them) even as preventing these time-eating and schema-changing operations from being to be had to many users. Separating index and useful resource authorization lets in a user to build an index on current relations, say, for optimization functions, but allows us to deny that person the proper to create new family members.

Q50. Suppose That There Is A Database System That Never Fails. Is A Recovery Manager Required For This System?

Even in this situation the healing manager is needed to carry out roll-returned of aborted tractions.