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Oracle Architecture Interview Questions & Answers - Learning Mode

Oracle Architecture Interview Questions & Answers - Learning Mode

The Oracle database has a logical layer and a physical layer. The physical layer consists of the files that reside on the disk; the components of the logical layer map the data to these physical components.

Try Oracle Architecture Interview Questions & Answers - Exam Mode

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Oracle Architecture Interview Questions & Answers - Learning Mode
Try Oracle Architecture Interview Questions & Answers - Exam Mode
Question: What are the Large object types supported by Oracle?

Answer: Oracle provides six data types for storing LOBs:

? CLOB and LONG for large fixed-width character data

? NCLOB for large fixed-width national character set data

? BLOB and LONG RAW for storing unstructured data

? BFILE for storing unstructured data in operating system files

LONG and LONG RAW data types were previously used for unstructured data, such as binary images, documents, or geographical information, and are primarily provided for backward compatibility. Source:
Question: Describe the different type of Integrity Constraints supported by ORACLE ?

Answer: 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. Source:
Question: Explain in brief oracle database objects.

Answer: Tables
Oracle stores information in the form of tables. For eg you can have a table named as climate in which you can store information about the climate of a place in the form of columns which could be the temperature, name of the place, date, humidity, etc.

In the terms of a relational database, one can call a table as an entity and the columns as it attributes.
2. Indexes

Indexing is a concept of listing of keywords accompanied by the location of information of the subject Source:
Question: Explain different types of segment. Data segment, Index segment, Rollback segment and temporary segment.

Answer: There are four types of segments used in Oracle databases:

- data segments
- index segments
- rollback segments
- temporary segments

Data Segments:
There is a single data segment to hold all the data of every non clustered table in an oracle database. This data segment is created when you create an object with the CREATE TABLE/SNAPSHOT/SNAPSHOT LOG command. Also, a data segment is created for a cluster when a CREATE CLUSTER command is issued.

The storage paramet Source:
Question: What is SQL Loader? Explain the files used by SQL Loader to load file. i.e Loader control file, Input datafile, Log File, Bad File, Discard file

Answer: SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database. SQL*Loader supports various load formats, selective loading, and multi-table loads.

When a control file is fed to an SQL*Loader, it writes messages to the log file, bad rows to the bad file and discarded rows to the discard file.

Control file
The SQL*Loader control file contains information that describes how the data will be loaded. It contains the table name, column datatypes Source:
Question: Explain SGA memory structures: Shared Pool, Database buffer Cache, Redo log Cache, Large Pool Java Pool.

Answer: SGA (System Global Area) is a dynamic memory area of an Oracle Server. In SGA,the allocation is done in granuels. The size of the SGA is dependent on SGA_MAX_SIZE parameter.

The memory structures contained by SGA are:-

Shared Pool -
this memory structure is divided into two sub-structures which are Library Cache and Data Dictionary Cache for storing recently used PL/SQL statements and the recent data definitions. The maximum size of the Shared Pool depends on the SHARED_POOL_SIZ Source:
Question: Describe Oracle architecture in brief.

Answer: The Oracle database has:

- Logical layer: The components of the logical layer map the data to these physical components

- Physical layer: The physical layer consists of the files that reside on the disk

Tablespaces and Datafiles
The database is divided into one or more logical pieces known as tablespaces. A tablespace is used to logically group data together

The Database Schema: A collection of logical-structure objects, known as schema objects.

These schema Source:
Question: What are the Large object types supported by Oracle?

Answer: Oracle provides six data types for storing LOBs:
CLOB and LONG for large fixed-width character data
NCLOB for large fixed-width national character set data
BLOB and LONG RAW for storing unstructured data
BFILE for storing unstructured data in operating system files
LONG and LONG RAW data types were previously used for unstructured data such as binary images documents or geographical information and are primarily provided for backward compatibility. These data types are superseded Source:
Question: what is the differnece between materialized view and snapshot

Answer: A materialized view is a replica of a target master from a singlepoint in time. The concept was first introduced with Oracle7 termed asSNAPSHOT. In Oracle release 7.1.6 snapshots were enhanced to enableDMLs along with a new terminology, updatable snapshots. With Oracle8.1.6 snapshots started to be used in data warehouse environments so anew terminology materialized view was introduced to address bothdistributed and data warehouse materialized views. Source:
Question: What are the Characteristics of Data Files

Answer: A data file is created when a 'create tablespace' or 'alter tablespace' command is executed. Creating a data file of size 10MB actually allocates 10MB space on the hard disk.

If a tablespace is declared to contain 100 data files one slot per data file is reserved in the control file.

There are four types of data files -- system data files application (or user) data files temporary data files (used by oracle to store temp data while executing complex SQL statements) Source:
Question: What is the physical and logical structure of oracle?

Answer: Logical Database structures
Logical structures include tablespaces, schema objects, data blocks, extents and segments.

Database is logically divided into one or more tablespaces. Each tablespace creates one or more datafiles to physically store data.

Schema objects
Schema objects are the structure that represents database's data. Schema objects include structures such as tables, views, sequences, stored procedures, indexes, synonyms, clusters and database Source:
Question: what is the difference between SID and Global Database Name ?

Answer: SID (System Identifier) : A SID (almost) uniquely identifies an instance. Actually, $ORACLE_HOME, $ORACLE_SID and $HOSTNAME identify an instance uniquely. The SID is 64 characters, or less; at least on Oracle 9i. The system identifier is included in the CONNECT_DATA parts of the connect descriptors in a tnsnames.ora file. The SID defaults to the database name.

Global Database Name : A database is uniquely identified by a global database name. Usually, a global database name has the for Source:
Question: What is a Data Dictionary ?

Answer: 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.

Question: What is the function of SMON?

Answer: The SMON background process performs all system monitoring functions on the oracle database.

Each time oracle is re-started, SMON performs a warm start and makes sure that the transactions that were left incomplete at the last shut down are recovered.

SMON performs periodic cleanup of temporary segments that are no longer needed. Source:
Question: Physical database structure

Answer: The physical database structure comprises of datafiles, redo log files and control files

Datafiles contain database's data. The data of logical data structures such as tables and indexes is stored in datafiles of the database. One or more datafiles form a logical unit of database storage called a tablespace.

Redo log files
The purpose of these files is to record all changes made to data. These files protect database against failures.

Control files
Con Source:
Question: SGA definition files

Answer: System Global Area
The System Global Area (SGA) is a shared memory region that contains data and control information for one Oracle instance. When an instance starts, the SGA is allocated by Oracle and is deallocated when the instance shuts down. Every instance has an own SGA.

Online Users share the data in the SGA.

The information stored in the SGA is divided into memory structures like:

* The database buffers
* Redo log buffer
* The shared poo Source:
Question: Explain the categories of oracle processes i.e. user, data writing processes, logging processes and monitoring processes.

Answer: * User process ? User process is used in invocation of application software.
* Data writing process - A database writer process is used to write buffer content into a datafile. They are specifically used to write ?dirty block? to data files from the buffer.
* Logging processes - Log writer is used to write the redo log buffer from system global area to online redo log file. Only those redo entries are written hat have been copied into the buffer since the last time it wrote.
Question: Explain the types of data files used by the oracle RDBMS.

Answer: Online redo log files
A control file contains information such as location of redo log files, backup data and redo log information.

The control file is updated to reflect the structure changes every time a datafile or a redo log file is added or dropped from the database. These records are necessary to identify datafiles and redo log files during startup and recovery.

Archive log files
Archived log files are redo logs that Oracle fills with redo entries that are rendered inac Source:
Question: What is the use of Redo Log Information ?

Answer: Oracle maintains logs of all transactions against the databse. These transactions are recorded in files called Online Redo log files.These logs are used to recover the database's transaction in their proper order in the evnt of database crash. The redo log information is stored in Redo log file which is external to the datafilesEach database have two or more online redo log files. oracle writes tedo log file in cyclic order after the first log is filled it writes to the second log files unti Source:
Question: Explain the areas of memory used by oracle, i.e. Software code area, system global area (SGA), program global area(PGA), sort area.

Answer: Software area code: - It is a protected location that is used to store oracle code that is supposed to be run. The location is different from users' programs. The software area code is read only and can be shared or nonshared.

System global area: - SGA is used to store data and control information of an Oracles database instance when started. Each instance has its own SGA. SGA is read write. It comprises data structures like Redo buffer, Java pool, Streams pool etc.

Program glo Source:

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