Oracle Questions

It is virtual table which is defined as a stored procedure based on one or more tables.

- Mask the real name and owner of an object.
- Provide public access to an object
- Provide location transparency for tables, views or program units of a remote database.
- Simplify the SQL statements for database users.

- These are the Logical Storage Units into which a database is divided.
- It is used to group together the related logical structures.

Primary key constraint ensures that the column(s) always has a unique value to identify the record.
Example:
Below, the primary key is created for column id with name prim_id.
create table employee ( id number NOT NULL, Name varchar(200) Constraint prim_id primary key(id) );

The following are the areas of concern for tuning:

- Memory Usage

- Data Storage

- Data Manipulation

- Physical Storage

- Logic Storage

- Network Traffic

Tuning Memory Usage: In Oracle 10g, we can use the Automatic Workload Repository (AWR) toolset to gather and manage statistical data but in case of Oracle 11g, we can use new initialization parameters such as MEMORY_TARGET to further control the overall memory used by Oracle. It helps us to tune the database automatically when we don’t have time to read the AWR report.

Tuning Data Manipulation: There are two ways to tune Data manipulation in Oracle one way is through Conventional Path mode and second is Direct Path mode.

Tuning Physical Storage: We need to tune the physical storage because it limits the disk in database. This can be done by: Distributing I/O, Striping and Mirroring.

A synonym can be called as an alias for a table, view, sequence or program unit. It is basically of two types:
- Private - Only the owner can access it.
- Public - Can be accessed by any database user.

Peoplesoft Database is similar to other database which is used to store data. Peoplesoft database stores data in a table format for system PeopleTools and Application tables. This is independent of the process you use to retrieve that data from PeopleSoft. Inside PeopleSoft database, only three types of tables reside inside the schema: System Catalog tables, PeopleTools tables, and Application data tables. Two of these table types, System Catalog and PeopleTools tables, can be referred to as metadata tables; users make use of Application data tables to store the data they need for their processes.

Oracle supports 3 transaction isolation levels: 

- Read committed (default)

- Serializable transactions

- Read only