ORACLE DBA BLOG

    Hot Backup : A hot backup is taken when the database needs  totally open and available to its users . It is an online backup. All files of the database are copied and there may be changes to the database during the copy. For the hot backup the database must be running in the ARCHIVELOG Mode. The benefit of taking a hot backup is that the database is available for use while the backup is occurring and one can recover the database to any point in time. For Hot Backup  the database must be informed when the backup is starting and when it is going to complete.    Alter database begin backup  Alter database end backup    Backup Procedure :  Gather all the Info for the backup Purpose .  select name from v$datafile ; select * from v$controlfile ; select name from v$logfile ; select NAME from v$archived_log ; create pfile from spfile ;   Perform a log switch and note down the old and current log  sequence of database...

 Cold Backup :  A cold backup is done when there is no user activity going on with the system. Also called as offline backup, is taken when the database is not running and no users are logged in. all files of the database are copied and no changes during the copy are made. Cold backup can be preformed when Database is in archive mode as well as Non archive log mode  . Backup Strategy :  Gather all the details of physical files (CRD) files in  database . redo log files are online redo log and archived redo log ones .   Select file_name,tablespace_name from dba_data_files  ; select * from v$controlfile  select member from v$logfile ; select name from v$archived_Log ;  create pfile from spfile  Backup  the contol file manually . alter database backup controlfile to trace as '/tmp/coldbackup_controlfile.sql' ;     Stop all the DB services (Database ,Listener)on source DB Server. Copy all the files(Datafiles,redo...

  Tables ·          Tables are the basic unit of data storage in an Oracle Database. Data is stored in rows and columns. ·          You define a table with a table name, such as employees , and a set of columns. You give each column a column name, such as employee_id , last_name , and job_id ; a datatype, such as VARCHAR2 , DATE , or NUMBER ; and a width. ·          The width can be predetermined by the datatype, as in DATE . If columns are of the NUMBER datatype, define precision and scale instead of width. ·            A row is a collection of column information corresponding to a single record. ·          You can specify rules for each column of a table. These rules are called integrity constraints. One example is a NOT NULL integrity constraint. This constraint f...

 Linux : Linux is one of popular version of UNIX operating System It is the interface between the user and the hardware. It performs a variety of tasks including file handling, memory management, controlling hardware devices, process management and many more. There are various versions of Unix: Solaris Unix, HP Unix, AIX, etc. Linux is is free and open source. Unix/Linux   is popular in enterprise-level because it supports multiple user environment. Linux Operating System has primarily three components. 1.       Kernel 2.       Shell Kernel: Kernel is the core of the operating system that controls all the tasks of the system . It consists of various modules, and it interacts directly with the underlying hardware. Kernel provides the required abstraction to hide low level hardware details to system or application programs.   It contains all the basic, low-level things that are needed to make the compute...