Advantages and Disadvantages of DBMSs
Disadvantages
The disadvantages of the database approach are summarized in Table 1.3.
Complexity
The provision of the functionality we expect of a good DBMS makes the DBMS an
extremely complex piece of software. Database designers and developers, the data and
database administrators, and end-users must understand this functionality to take full
advantage of it. Failure to understand the system can lead to bad design decisions, which
can have serious consequences for an organization.
Size
The complexity and breadth of functionality makes the DBMS an extremely large piece of
software, occupying many megabytes of disk space and requiring substantial amounts of
memory to run efficiently.
Cost of DBMSs
The cost of DBMSs varies significantly, depending on the environment and functionality
provided. For example, a single-user DBMS for a personal computer may only cost
US$100. However, a large mainframe multi-user DBMS servicing hundreds of users can
be extremely expensive, perhaps US$100,000 or even US$1,000,000. There is also the
recurrent annual maintenance cost, which is typically a percentage of the list price.
Additional hardware costs
The disk storage requirements for the DBMS and the database may necessitate the purchase
of additional storage space. Furthermore, to achieve the required performance, it may
be necessary to purchase a larger machine, perhaps even a machine dedicated to running
the DBMS. The procurement of additional hardware results in further expenditure.
Cost of conversion
In some situations, the cost of the DBMS and extra hardware may be insignificant
compared with the cost of converting existing applications to run on the new DBMS and
hardware. This cost also includes the cost of training staff to use these new systems, and
possibly the employment of specialist staff to help with the conversion and running of
the system. This cost is one of the main reasons why some organizations feel tied to their
current systems and cannot switch to more modern database technology. The term legacy
system is sometimes used to refer to an older, and usually inferior, system.
Performance
Typically, a file-based system is written for a specific application, such as invoicing. As a
result, performance is generally very good. However, the DBMS is written to be more
general, to cater for many applications rather than just one. The effect is that some applications
may not run as fast as they used to.
Higher impact of a failure
The centralization of resources increases the vulnerability of the system. Since all users
and applications rely on the availability of the DBMS, the failure of certain components can
bring operations to a halt.
Disadvantages
The disadvantages of the database approach are summarized in Table 1.3.
Complexity
The provision of the functionality we expect of a good DBMS makes the DBMS an
extremely complex piece of software. Database designers and developers, the data and
database administrators, and end-users must understand this functionality to take full
advantage of it. Failure to understand the system can lead to bad design decisions, which
can have serious consequences for an organization.
Size
The complexity and breadth of functionality makes the DBMS an extremely large piece of
software, occupying many megabytes of disk space and requiring substantial amounts of
memory to run efficiently.
Cost of DBMSs
The cost of DBMSs varies significantly, depending on the environment and functionality
provided. For example, a single-user DBMS for a personal computer may only cost
US$100. However, a large mainframe multi-user DBMS servicing hundreds of users can
be extremely expensive, perhaps US$100,000 or even US$1,000,000. There is also the
recurrent annual maintenance cost, which is typically a percentage of the list price.
Additional hardware costs
The disk storage requirements for the DBMS and the database may necessitate the purchase
of additional storage space. Furthermore, to achieve the required performance, it may
be necessary to purchase a larger machine, perhaps even a machine dedicated to running
the DBMS. The procurement of additional hardware results in further expenditure.
Cost of conversion
In some situations, the cost of the DBMS and extra hardware may be insignificant
compared with the cost of converting existing applications to run on the new DBMS and
hardware. This cost also includes the cost of training staff to use these new systems, and
possibly the employment of specialist staff to help with the conversion and running of
the system. This cost is one of the main reasons why some organizations feel tied to their
current systems and cannot switch to more modern database technology. The term legacy
system is sometimes used to refer to an older, and usually inferior, system.
Performance
Typically, a file-based system is written for a specific application, such as invoicing. As a
result, performance is generally very good. However, the DBMS is written to be more
general, to cater for many applications rather than just one. The effect is that some applications
may not run as fast as they used to.
Higher impact of a failure
The centralization of resources increases the vulnerability of the system. Since all users
and applications rely on the availability of the DBMS, the failure of certain components can
bring operations to a halt.
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