Database Reference
In-Depth Information
Integrity Considerations
As you have seen, the transaction-processing database system is subject to poten-
tial integrity problems. Users may be exposed to inconsistent, incorrect, and invalid
data. Integrity functions in the database management system must be able to pre-
serve the integrity of the database by performing the following actions:
•
Monitor and scrutinize all transactions, especially those with database updates
•
Detect any data integrity violations by transactions
•
If a violation is detected, take appropriate action such as
•
Rejection of the operation
•
Reporting of the violation
•
Correction of error condition, if possible
Specific components exist in the DBMS for preserving database integrity. Figure
15-4 presents an overview of integrity components. Each component performs a
particular set of functions.
While processing concurrent transactions in a database environment, the opera-
tions of different transactions interleave with one another. Integrity problems might
arise because of such interleaved processing of transactions. We will discuss con-
currency control in detail in subsequent sections.
Database failures result in potential integrity problems. The transactions that are
in flight during a disk crash may not complete all the database updates. They may
not have a chance to roll back the incomplete updates. We will examine database
failures in depth in another subsequent section.
Here, let us turn our attention to a few other types of integrity problems and look
at the solution options. For our discussion, we will adopt a very common example
of a suppliers and parts database schema. Figure 15-5 presents the relational tables
of the suppliers and parts database.
DBMS
Database
Engine
Transaction
Manager
Access
Manager
DATABASE
DATA
DICTIONARY
Transaction
Scheduler
File
Manager
Recovery
Manager
Buffer
Manager
Figure 15-4
DBMS integrity components.
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