is a component of a data model that defines the boundaries of a database, such as maximum and minimum values allowed for a field, constraints, and access methods.

Data base administrator

Explanation:

The data base administrator is a component of a data model that defines the boundaries of a database, such as maximum and minimum values allowed for a field , constraints and access methods. Database is structured from of data sets.  

The data in database use to come from different sources that data must have some boundaries. Database administrator is a part of DBMS. The authorized DBA is responsible for the integrity of data and keeping the data in good manner so at the time of need the data could be accessed rightly. Storage of data has to be  done in a way that at time of use or at the time of retrieval the data must be accessed frequently and easily.  

Database administrator is responsible to put constraint on the database, for example a person could enter how many digits or alphabets in the required fields or records. Otherwise user could enter irrelevant and lengthy data in the fields so it would be hard to manage data on server due to shortage of the memory. By putting such constraints the size of data could be managed and relevant data could be saved. Secondly, constraints use to be put for security purpose to keep information confidential and secure the  certain constraints are mandatory and the data base administrator is responsible for such constraints.

Once the user use to store data on database the data safety and integrity is most important for them. So that DBA will arrange the data in organised form which will give quick access and data length will be managed properly so user could not enter lengthy data to full the repository. DBA put security constraint as well for the satisfaction of user and secure use of the database.

So we could say that dba is most important part of DBMS of any organization.

d. use a mixture of external and internal links

explanation:

answer; numerous occupation(s);