What is kept in the Database Buffer Cache?

What is kept in the Database Buffer Cache?
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1 Answer

Answer :

The database buffer cache is the portion of the SGA that holds copies of data blocks read from datafiles. All user processes concurrently connected to the instance share access to the database buffer cache.
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Related questions

How would you go about increasing the buffer cache hit ratio?

Description : How would you go about increasing the buffer cache hit ratio?

Last Answer : Use the buffer cache advisory over a given workload and then query the v$db_cache_advice table. If a change was necessary then I would use the alter system set db_cache_size command.

What is DB Buffer Cache Advisor?

Description : What is DB Buffer Cache Advisor?

Last Answer : The Buffer Cache Advisor provides advice on how to size the Database Buffer Cache to obtain optimal cache hit ratios. Member of Performance Advisors --> Memory Advisor pack.

What is dictionary cache ?

Description : What is dictionary cache ?

Last Answer : Dictionary cache is information about the databse objects stored in a data dictionary table.

Translation Look-aside Buffer(TLB) is (A) a cache-memory in which item to be searched is compared one-by-one with the keys. (B) a cache-memory in which item to be searched is compared with all the keys simultaneously. (C) an associative memory in which item to be searched is compared one-by-one with the keys. (D) an associative memory in which item to be searched is compared with all the keys simultaneously.

Description : Translation Look-aside Buffer(TLB) is (A) a cache-memory in which item to be searched is compared one-by-one with the keys. (B) a cache-memory in which item to be searched is compared with ... keys. (D) an associative memory in which item to be searched is compared with all the keys simultaneously.

Last Answer : (D) an associative memory in which item to be searched is compared with all the keys simultaneously.

The virtual address generated by a CPU is 32 bits. The Translation Lookaside Buffer (TLB) can hold total 64 page table entries and a 4-way set associative (i.e. with 4- cache lines in the set). The page size is 4 KB. The minimum size of TLB tag is (A) 12 bits (B) 15 bits (C) 16 bits (D) 20 bits

Description : The virtual address generated by a CPU is 32 bits. The Translation Lookaside Buffer (TLB) can hold total 64 page table entries and a 4-way set associative (i.e. with 4- cache lines in the set). The page size is 4 KB. The minimum size of TLB tag is (A) 12 bits (B) 15 bits (C) 16 bits (D) 20 bits

Last Answer : (C) 16 bits Explanation: VirtualAddress = 32 bits PageSize = 4KB = 12 bits therefore : VPNTag = 20 bits, OffsetTag = 12 bits TLBEntryLength = VPNTag = 20 bits TotalTLBEntries = 64, 4-way implies ... therefore : TLBIndex = 4 bits TLBTag = TLBEntryLength - TLBIndex = 20 - 4 = 16 bits

What is the name of a memory buffer used to accommodate a speed differential ? (1) Cache (2) Stack Pointer (3) Accumulator (4) Disc

Description : What is the name of a memory buffer used to accommodate a speed differential ? (1) Cache (2) Stack Pointer (3) Accumulator (4) Disc

Last Answer : Cache

What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

Description : What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

Last Answer : 1,000,00

What is meant by redo log buffer ?

Description : What is meant by redo log buffer ?

Last Answer : Changes made to entries are written to the on-line redo log files. So that they can be used in roll forward operations during database recoveries. Before writing them into the redo log files ... buffers in SGA and LGWR will write into files frequently. LOG_BUFFER parameter will decide the size.

What is Buffer Manager?

Description : What is Buffer Manager?

Last Answer : It is a program module, which is responsible for fetching data from disk storage into main memory and deciding what data to be cache in memory.

Name the buffer in which all the commands that are typed in are stored

Description : Name the buffer in which all the commands that are typed in are stored

Last Answer : ‘Edit’ Buffer

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Description : How does one manage Oracle database users? (for DBA

Last Answer : Oracle user accounts can be locked, unlocked, forced to choose new passwords, etc. For example, all accounts except SYS and SYSTEM will be locked after creating an Oracle9iDB database using the DB ... locked users account ALTER USER scott PASSWORD EXPIRE; -- Force user to choose a new password

How does one manage Oracle database users? (for DBA

Description : How does one manage Oracle database users? (for DBA

Last Answer : Oracle user accounts can be locked, unlocked, forced to choose new passwords, etc. For example, all accounts except SYS and SYSTEM will be locked after creating an Oracle9iDB database using the ... from SYS.V$BH log buffer spaces Increase LOG_BUFFER parameter or move log files to faster disks

How does one backup a database using the export utility? (for DBA

Description : How does one backup a database using the export utility? (for DBA

Last Answer : Oracle exports are "logical" database backups (not physical) as they extract data and logical definitions from the database into a file. Other backup strategies normally back-up the physical data ... exports include more information about the database in the export file than user level exports.

What strategies are available for backing-up an Oracle database? (for DBA

Description : What strategies are available for backing-up an Oracle database? (for DBA

Last Answer : The following methods are valid for backing-up an Oracle database: Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file. ... , etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.

Why and when should I backup my database? (for DBA

Description : Why and when should I backup my database? (for DBA

Last Answer : Backup and recovery is one of the most important aspects of a DBAs job. If you lose your company's data, you could very well lose your job. Hardware and software can always be ... things that will get you. Most failed recoveries are a result of organizational errors and miscommunications.

What are the roles and user accounts created automatically with the database?

Description : What are the roles and user accounts created automatically with the database?

Last Answer : DBA - role Contains all database system privileges. SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database's dictionary ... administrative information and internal tables and views used by oracle tools are created using this username.

What are the responsibilities of a Database Administrator ?

Description : What are the responsibilities of a Database Administrator ?

Last Answer : Installing and upgrading the Oracle Server and application tools. Allocating system storage and planning future storage requirements for the database system. Managing primary database structures ... tape Backing up and restoring the database. Contacting Oracle Corporation for technical support.

How does one create a standby database? (for DBA)

Description : How does one create a standby database? (for DBA)

Last Answer : While your production database is running, take an (image copy) backup and restore it on duplicate hardware. Note that an export will not work!!! On your standby database, issue ... the standby database, stop the recovery process and activate it: ALTER DATABASE ACTIVATE STANDBY DATABASE;

Name two files used for network connection to a database.

Description : Name two files used for network connection to a database.

Last Answer : TNSNAMES.ORA and SQLNET.ORA

When creating a user, what permissions must you grant to allow them to connect to the database?

Description : When creating a user, what permissions must you grant to allow them to connect to the database?

Last Answer : Grant the CONNECT to the user.

Name a tablespace automatically created when you create a database.

Description : Name a tablespace automatically created when you create a database.

Last Answer : The SYSTEM tablespace.

How would you determine the time zone under which a database was operating?

Description : How would you determine the time zone under which a database was operating?

Last Answer : select DBTIMEZONE from dual;

Where would you look for errors from the database engine?

Description : Where would you look for errors from the database engine?

Last Answer : In the alert log.

You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?

Description : You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?

Last Answer : I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.

What is network database link?

Description : What is network database link?

Last Answer : 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.

What is public database link?

Description : What is public database link?

Last Answer : 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.

What is private database link?

Description : What is private database link?

Last Answer : 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.

What are the types of database links?

Description : What are the types of database links?

Last Answer : Private database link, public database link & network database link.

What is Database Link ?

Description : What is Database Link ?

Last Answer : A database link is a named object that describes a "path" from one database to another.

What are the steps involved in Database Shutdown ?

Description : What are the steps involved in Database Shutdown ?

Last Answer : Close the Database, Dismount the Database and Shutdown the Instance.

What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode ?

Description : What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode ?

Last Answer : Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible only in ARCHIVELOG mode.

What are the different modes of mounting a Database with the Parallel Server ?

Description : What are the different modes of mounting a Database with the Parallel Server ?

Last Answer : Exclusive Mode If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database. Parallel Mode If the first instance that mounts a database is started in parallel mode, other instances that are started in parallel mode can also mount the database.

Can Full Backup be performed when the database is open ?

Description : Can Full Backup be performed when the database is open ?

Last Answer : No.

What are the steps involved in Database Startup ?

Description : What are the steps involved in Database Startup ?

Last Answer : Start an instance, Mount the Database and Open the Database. Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo ... Resolving any pending distributed transactions undergoing a two- phase commit at the time of the instance failure.

Can you store pictures in database? How?

Description : Can you store pictures in database? How?

Last Answer : Yes , in long Raw datatype.

Can U disable database trigger? How?

Description : Can U disable database trigger? How?

Last Answer : Yes. With respect to table ALTER TABLE TABLE [[ DISABLE all_trigger ]]

Who created all these users in my database?/ Can I drop this user? (for DBA

Description : Who created all these users in my database?/ Can I drop this user? (for DBA

Last Answer : Oracle creates a number of default database users or schemas when a new database is created. Below are a few of them: SYS/CHANGE_ON_INSTALL or INTERNAL Oracle Data Dictionary/ Catalog Created ... there should be no problem altering these users to use a different default and temporary tablespace.

How does one create and drop database users?

Description : How does one create and drop database users?

Last Answer : Look at these examples: CREATE USER scott IDENTIFIED BY tiger -- Assign password DEFAULT TABLESACE tools -- Assign space for table and index segments TEMPORARY TABLESPACE temp; -- Assign sort space ... give the user some space quota on its tablespaces: ALTER USER scott QUOTA UNLIMITED ON tools;

What are Database Triggers and Stored Procedures

Description : What are Database Triggers and Stored Procedures

Last Answer : Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table. Database triggers have the values old and new to ... procedures is that many users can use the same procedure in compiled and ready to use format.

What is a database link ?

Description : What is a database link ?

Last Answer : Database Link is a named path through which a remote database can be accessed.

Difference between database triggers and form triggers?

Description : Difference between database triggers and form triggers?

Last Answer : Data base trigger(DBT) fires when a DML operation is performed on a data base table. Form trigger(FT) Fires when user presses a key or navigates between fields on the screen -Can be row ... other database triggers to fire.Can cause other database triggers to fire, but not other form triggers.

Can you use a commit statement within a database trigger?

Description : Can you use a commit statement within a database trigger?

Last Answer : No

What are different Oracle database objects?

Description : What are different Oracle database objects?

Last Answer : TABLES -VIEWS INDEXES -SYNONYMS -SEQUENCES -TABLESPACES etc

What is Database Trigger ?

Description : What is Database Trigger ?

Last Answer : A Database Trigger is procedure (set of SQL and PL/SQL statements) that is automatically executed as a result of an insert in,update to, or delete from a table.

What are the uses of Database Trigger ?

Description : What are the uses of Database Trigger ?

Last Answer : Database triggers can be used to automatic data generation, audit data modifications, enforce complex Integrity constraints, and customize complex security authorizations.

What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?

Description : What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?

Last Answer : Procedures and Functions,Packages and Database Triggers.

What is a database trigger ? Name some usages of database trigger ?

Description : What is a database trigger ? Name some usages of database trigger ?

Last Answer : Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.

How many types of database triggers can be specified on a table ? What are they ?

Description : How many types of database triggers can be specified on a table ? What are they ?

Last Answer : Insert Update Delete Before Row o.k. o.k. o.k. After Row o.k. o.k. o.k. Before Statement o.k. o.k. o.k. After Statement o.k. o.k. o.k. If FOR EACH ROW clause is ... for each Row affected by the statement. If WHEN clause is specified, the trigger fires according to the returned Boolean value.

Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?

Description : Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?

Last Answer : It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.

What is a Virtual Private Database? (for DBA

Description : What is a Virtual Private Database? (for DBA

Last Answer : Oracle 8i introduced the notion of a Virtual Private Database (VPD). A VPD offers Fine-Grained Access Control (FGAC) for secure separation of data. This ensures that users only have ... the DBMS_RLS (Row Level Security) package. Select from SYS.V$VPD_POLICY to see existing VPD configuration.