Disadvantages of indexed file organization

The Turkish vehicle plate numbering system is NOT suitable for using relative files because it contains alphabetic parts eg. Having declared the "PLATE" field as the key field, now, given a plate number, a program which has declared an indexed file with RANDOM access mode, can find the corresponding record very quickly if the does exist, this condition will also be detected very quickly. Knowing that no two vehicles have the same plate number unique , the plate number is certainly a very good choice for the key.

However, suppose that the program you have to write is also expected to find records for vehicles of a certain brand very quickly. You can declare as many alternate keys your program requires. More alternate keys you have, more extra data structures will be required and slower be your program. Therefore certain attention should be paid before assigning alternate keys.

You should avoid unnecessary alternate keys. When you need to access the file with the primary key, you just move the key value to the primary key field of the record and issue a READ statement. Ask a Question. El Lly answered. Hello, There are several factors to consider that pertain to the advantages and disadvantages of indexed sequential file organisation.

Direct access file organization Direct access file is also known as random access or relative file organization. In direct access file, all records are stored in direct access storage device DASD , such as hard disk. The records are randomly placed throughout the file. The records does not need to be in sequence because they are updated directly and rewritten back in the same location.

This file organization is useful for immediate access to large amount of information. It is used in accessing large databases. It is also called as hashing. Advantages of direct access file organization Direct access file helps in online transaction processing system OLTP like online railway reservation system. In direct access file, sorting of the records are not required. It accesses the desired records immediately.

It updates several files quickly. It has better control over record allocation. Disadvantages of direct access file organization Direct access file does not provide back up facility. It is expensive. Insertion of new record — Let us assume that there is a preexisting sorted sequence of four records R1, R3, and so on upto R7 and R8. Suppose a new record R2 has to be inserted in the sequence, then it will be inserted at the end of the file and then it will sort the sequence.

Simple design. Files can be easily stored in magnetic tapes i. Cons —. Skip to content. Change Language. Related Articles. Relational model relational algebra, tuple calculus. Database design integrity constraints, normal forms. Query languages SQL.