Explore topic-wise InterviewSolutions in .

There are TABLESPACES and DATABASE’s SCHEMA OBJECTS.

There are tablespaces and database’s schema objects.

A database is DIVIDED into LOGICAL Storage UNIT called tablespaces. A tablespace is used to grouped related logical structures TOGETHER.

A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.

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.

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.

Each DATABASES logically divided into ONE or more tablespaces one or more DATA files are explicitly CREATED for each TABLESPACE.

Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.

SCHEMA OBJECTS are the logical structures that directly refer to the database’s data. Schema objects include tables, views, sequences, synonyms, indexes, CLUSTERS, database triggers, PROCEDURES, FUNCTIONS packages and database links.

Schema objects are the logical structures that directly refer to the database’s data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.

Yes.

Yes.

Yes.

Yes.

A table is the basic UNIT of DATA storage in an Oracle database. The tables of a database hold all of the user ACCESSIBLE data. Table data is stored in ROWS and columns.

A table is the basic unit of data storage in an Oracle database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

A view is a VIRTUAL table. Every view has a query attached to it. (The query is a SELECT statement that identifies the COLUMNS and ROWS of the table(s) the view uses.)

A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

VIEWS do not CONTAIN or STORE DATA.

Views do not contain or store data.

•  PROVIDE an ADDITIONAL level of table security, by restricting access to a predetermined set of rows and columns of a table.
•  Hide data complexity.
•  Simplify commands for the user.
•  Present the data in a different PERSPECTIVE from that of the BASE table.
•  STORE complex queries.

A sequence GENERATES a serial LIST of unique NUMBERS for NUMERICAL COLUMNS of a database’s tables.

A sequence generates a serial list of unique numbers for numerical columns of a database’s tables.

A SYNONYM is an ALIAS for a table, view, SEQUENCE or PROGRAM UNIT.

A synonym is an alias for a table, view, sequence or program unit.

Only its OWNER can ACCESS a PRIVATE SYNONYM.

Only its owner can access a private synonym.

Any DATABASE USER can ACCESS a PUBLIC SYNONYM.

Any database user can access a public synonym.

- 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.

- 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.

INDEXES are automatically MAINTAINED and USED by ORACLE. Changes to table data are automatically INCORPORATED into all relevant indexes.

Indexes are automatically maintained and used by Oracle. Changes to table data are automatically incorporated into all relevant indexes.

The RELATED COLUMNS of the TABLES in a cluster are CALLED the cluster key.

The related columns of the tables in a cluster are called the cluster key.

A CLUSTER with an INDEX on the cluster KEY.

A cluster with an index on the cluster key.

Hash clusters are BETTER choice when a table is often queried with equality queries. For such queries the SPECIFIED cluster key VALUE is HASHED. The resulting hash key value POINTS directly to the area on disk that stores the specified rows.

Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.

Private database LINK, public database link & NETWORK database link.

Private database link, public database link & network database link.

Private database link is created on behalf of a SPECIFIC user. A private database link can be USED only when the OWNER of the link specifies a global OBJECT name in a SQL statement or in the definition of the owner’s VIEWS or procedures.

Private database link is created on behalf of a specific user. A private database link can be used only when the owner of the link specifies a global object name in a SQL statement or in the definition of the owner’s views or procedures.

Public database link is created for the special user GROUP PUBLIC. A public database link can be used when any user in the associated database SPECIFIES a GLOBAL object name in a SQL STATEMENT or object definition.

Public database link is created for the special user group PUBLIC. A public database link can be used when any user in the associated database specifies a global object name in a SQL statement or object definition.

Network database link is created and MANAGED by a network DOMAIN service. A network database link can be used when any user of any database in the network specifies a global object NAME in a SQL STATEMENT or object DEFINITION.

Network database link is created and managed by a network domain service. A network database link can be used when any user of any database in the network specifies a global object name in a SQL statement or object definition.

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’s data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.

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 data BLOCKS. Block size is specified in init.ora FILE and cannot be changed latter.

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 data blocks. Block size is specified in init.ora file and cannot be changed latter.

In circumstances, all of the data for a row in a table MAY not be able to fit in the same data block. When this occurs, the data for the row is STORED in a CHAIN of data block (ONE or more) RESERVED for that segment.

In circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs, the data for the row is stored in a chain of data block (one or more) reserved for that segment.

To GENERATE read-consistent database information during database RECOVERY and to rollback uncommitted transactions by the users.

To generate read-consistent database information during database recovery and to rollback uncommitted transactions by the users.

When the STATEMENT finishes execution, the TEMPORARY segment EXTENTS are released to the SYSTEM for future use.

When the statement finishes execution, the temporary segment extents are released to the system for future use.

Every ORACLE database has one or more physical data FILES. A database’s data files CONTAIN all the database data. The data of LOGICAL database structures such as tables and indexes is physically stored in the data files ALLOCATED for a database.

Every Oracle database has one or more physical data files. A database’s data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.

The primary FUNCTION of the REDO log is to record all changes MADE to data.

The primary function of the redo log is to record all changes made to data.

The information in a REDO log file is used only to recover the DATABASE from a system or MEDIA failure prevents database data from being WRITTEN to a database’s data FILES.

The information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a database’s data files.

- DATABASE name
- NAMES and LOCATIONS of a database’s files and redolog files.
- TIME stamp of database CREATION.

- Database name
- Names and locations of a database’s files and redolog files.
- Time stamp of database creation.

A database INSTANCE (Server) is a set of memory STRUCTURE and background processes that access a set of database FILES. The processes can be shared by all of the users.

The memory structure that is used to store the most QUERIED data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data FILE.

A database instance (Server) is a set of memory structure and background processes that access a set of database files. The processes can be shared by all of the users.

The memory structure that is used to store the most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

MULTIPLE INSTANCES ACCESSING the same DATABASE (only in multi-CPU ENVIRONMENTS)

Multiple instances accessing the same database (only in multi-CPU environments)

The set of OBJECTS owned by USER account is called the schema.

The set of objects owned by user account is called the schema.

The related columns of the tables are CALLED the cluster key. The cluster key is INDEXED using a cluster index and its VALUE is stored only once for MULTIPLE tables in the cluster.

The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.

The SYSTEM Global Area in an ORACLE database is the area in memory to facilitate the transfer of information between users. It HOLDS the most RECENTLY requested structural information between users. It holds the most recently requested structural information about the database. The structure is database buffers, dictionary cache, redo LOG buffer and shared pool area.

The System Global Area in an Oracle database is the area in memory to facilitate the transfer of information between users. It holds the most recently requested structural information between users. It holds the most recently requested structural information about the database. The structure is database buffers, dictionary cache, redo log buffer and shared pool area.

Shared pool in oracle CONTAINS CACHE information that collects, parses, INTERPRETS and executes SQL statements that goes against database. This shared pool ACTS LIKE a buffer for these SQL statements.

Shared pool in oracle contains cache information that collects, parses, interprets and executes SQL statements that goes against database. This shared pool acts like a buffer for these SQL statements.

It is area in memory that is used by a SINGLE Oracle USER PROCESS.

It is area in memory that is used by a single Oracle user process.

Data SEGMENT are the physical areas within a DATABASE BLOCK in which the data associated with TABLES and clusters are stored.

Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.

• Due to insufficient shared POOL size.
• MONITOR the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE.
• Database Logical & PHYSICAL Architecture

Database buffers are cache in the SGA USED to HOLD the data blocks that are read from the data segments in the database such as tables, INDEXES and clusters DB_BLOCK_BUFFERS PARAMETER in INIT.ORA DECIDES the size.

Database buffers are cache in the SGA used to hold the data blocks that are read from the data segments in the database such as tables, indexes and clusters DB_BLOCK_BUFFERS parameter in INIT.ORA decides the size.

Dictionary CACHE is INFORMATION about the database objects stored in a data dictionary table.

Dictionary cache is information about the database objects stored in a data dictionary table.

NUMBER of times processes repeatedly query the dictionary table is called RECURSIVE HINTS. It is due to the data dictionary cache is too small. By INCREASING the SHARED_POOL_SIZE PARAMETER we can optimize the size of data dictionary cache.

Number of times processes repeatedly query the dictionary table is called recursive hints. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of data dictionary cache.

- Export the user
- PERFORM import using the COMMAND imp system/manager file=export.dmp indexfile=newrite.sql. This will CREATE all definitions into newfile.sql.
- Drop necessary objects.
- RUN the script newfile.sql after altering the tablespaces.
- Import from the backup for the necessary objects.

- Export the user
- Perform import using the command imp system/manager file=export.dmp indexfile=newrite.sql. This will create all definitions into newfile.sql.
- Drop necessary objects.
- Run the script newfile.sql after altering the tablespaces.
- Import from the backup for the necessary objects.

SYSTEM – DATA dictionary tables.
DATA - Standard OPERATIONAL tables.
DATA2- Static tables USED for standard operations
INDEXES – Indexes for Standard operational tables.
INDEXES1 – Indexes of static tables used for standard operations.
TOOLS – Tools table.
TOOLS1 – Indexes for tools table.
RBS – Standard Operations Rollback Segments,
RBS1,RBS2 – Additional/Special Rollback segments.
TEMP – Temporary purpose TABLESPACE
TEMP_USER – Temporary tablespace for USERS.
USERS – User tablespace.

SYSTEM – Data dictionary tables.
DATA - Standard operational tables.
DATA2- Static tables used for standard operations
INDEXES – Indexes for Standard operational tables.
INDEXES1 – Indexes of static tables used for standard operations.
TOOLS – Tools table.
TOOLS1 – Indexes for tools table.
RBS – Standard Operations Rollback Segments,
RBS1,RBS2 – Additional/Special Rollback segments.
TEMP – Temporary purpose tablespace
TEMP_USER – Temporary tablespace for users.
USERS – User tablespace.

SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.

SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.

A FREE extent is a collection of continuous free blocks in tablespace. When a segment is DROPPED its extents are REALLOCATED and are marked as free.

A free extent is a collection of continuous free blocks in tablespace. When a segment is dropped its extents are reallocated and are marked as free.

PCTFREE PARAMETER
ROW size also REDUCES no of rows PER block.

PCTFREE parameter
Row size also reduces no of rows per block.