15 TOP Database Architecture Questions and Answers
1. What is an Oracle Rollback Segment?
A Database contains one or more Rollback Segments to temporarily store “undo” information.
2. What are the uses of Oracle Rollback Segment?
Rollback Segments are used :
To generate read consistent database information during database recovery to rollback uncommitted transactions for users
3. What are Oracle Schema Objects?
Schema objects are the logical structures that directly refer to the databases data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.
4. What is an Oracle Data Block?
ORACLE database’s data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.
Oracle database consists of logical storage place which is called as blocks and the bytes in a block is set through DB_BLOCK parameter in parameter file
5. Can objects of the same Schema reside in different tablespaces?
Yes objects of the same Schema reside in different tablespaces
6. What is the use of Oracle Control File?
When an instance of an ORACLE database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.
Control files is a binary file. Before database is opened it determines whether database is in valid state or not. If yes then database is opened.
7. Can a View based on another View in Oracle?
Yes a View based on another View in Oracle
8. What is the function of Redo Log in Oracle?
The Primary function of the redo log is to record all changes made to data
9. Describe the different type of Integrity Constraints supported by ORACLE?
NOT NULL Constraint – Disallows Nulls in a table’s column.
UNIQUE Constraint – Disallows duplicate values in a column or set of columns.
PRIMARY KEY Constraint – Disallows duplicate values and Nulls in a column or set of columns.
FOREIGN KEY Constrain – Require each value in a column or set of columns match a value in a related table’s UNIQUE or PRIMARY KEY.
CHECK Constraint – Disallows values that do not satisfy the logical expression of the constraint.
10. What is an Oracle Data Dictionary?
The data dictionary of an ORACLE database is a set of tables and views that are used as a read-only reference about the database.
It stores information about both the logical and physical structure of the database, the valid users of an ORACLE database, integrity constraints defined for tables in the database and space allocated for a schema object and how much of it is being used.
11. What is an Oracle SYSTEM tablespace and when is it Created?
Every ORACLE database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.
The SYSTEM tablespace is created automatically for each new Oracle database. It contains all the data dictionary objects for the entire database.
12. Can an Integrity Constraint be enforced on a table if some existing table data does not satisfy the constraint?
Yes we can enforce integrity constraint on a table if some existing table does not satisfy the constraint by using “ENABLE NOVALIDATE”
13. How to define Data Block size in Oracle?
A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE datablocks. Block size is specified in INIT.ORA file and can?t be changed latter.
A data block size is defined by DB_BLOCK parameter in pfile and there could be non standard block sizes supported by Oracle upto block size of 32bytes
Once set the block size could not be changed and the database has to be created again
14. What is an Integrity Constrains in Oracle?
An integrity constraint is a declarative way to define a business rule for a column of a table.
15. Can a Tablespace hold objects from different Schemes in Oracle?
Yes a Tablespace can hold objects from different Schemes in Oracle
16. What is an oracle database schema?
A schema is collection of database objects of a User.
A schema is collection of database objects of an user and is used synonym of an user.
Schema name = user name
17. What is an Oracle Data Segment?
Each Non-clustered table has a data segment. All of the table’s data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster’s data segment.
Latest Database Architecture Interview Questions and Answers