Oracle Interview Question

Quest1:-Which oracle process is responsible for fetch the data from database to data buffer?Ans:-If request data is not found in Data buffer then server process (not database writer)go to the database and fetch the data.Quest2::-During the database online backup. does data will write into datafile or not??Yes,data will be write into datafile. datafile headers freezes and all the modified blocks will be written to redo stream and when we issue end backup command then database will write modified blocks to datafiles by accessing redo files.Quest 3:-what we will do if our undo tablespace is full?Qust:-4 During starting of database if what will happen if SPfile is not found?BY default database read SPfile if its not found then it will read pfile.Quest 5:- When we create control from old controlfile, there have to option REUSE and SET. what is difference between?Quest 6:-what is database command to check the space in temp tablespace?Quest 7:- What are the various Backup strategies used in SAP ?(A) There are 3 Backup strategies in SAP i) Complete Backup:- Restore missing Database files from complete Backup, Restore Offline Redo Log files writte during and after this Backup. ii) Incremental Backup:- Restore missing Data files from last Full Backup, update them with restore from last Incremental Backup. iii)Partial Backup:- Replace complete backup with partial Backups , we need a longer time to perform a recovery from media crashQuest 8:- What are the situations in which DBWO writes dirty blocks to disks?If the number of scanned buffers reaches a certain thresh hold. At a specific time that is when check point occurs

Quest 9:- What are the conditions in which log writer writes redo log buffer data to online redo log files ?There 4 conditions: When transaction is committed. For every three seconds. When redo log is 1/3rd of full. When DBWR is about to write modified buffers to disk and some of the corresponding redo records have not at been written to online redo log i.e. write ahead logging.Quest 10:- How Listener work with database?Quest:11 What is the concept of log switching in oracle database?Oracle redo log files do not dynamically grow when more space is needed for redoentries; they have a fixed size (on SAP systems, typically 50 MB). When thecurrent online redo log file becomes full, the log writer process closes this file andstarts writing into the next one. This is called a log switch Quest 12:-What is the use of checkpoint?The term checkpoint has at least two different meanings.First, checkpoint is the event of writing all modified buffers in the buffer cache todata files with the database writer process.It updates the headers of all data files to record the details of the checkpoint.It writes information about the checkpoint position in the online redo loginto the control file.

Qest 13:-How we connect from OPS$ user?Cmd>>sqlplus / :-from this way it will connect from OPS$ user

Quest 14:-What is shutdown mode in oracle database?

NORMALNo new connections are allowed. Oracle waits for all currently connectedusers to disconnect from the database. Only after the last user hasdisconnected (in SAP system: all work processes have been stopped), Oracleshuts down the database: all files are closed, the database is dismounted, andthe instance is shut down.TRANSACTIONALNo new connections are allowed, and no new transactions are allowed to bestarted after the statement is issued. Oracle waits for all open transactionsto finish, then it disconnects all users (work processes in SAP system) andshuts down the database.IMMEDIATENo new connections are allowed, and no new transactions are allowed tobe started after the statement is issued. The PMON process ends all usersessions and performs a rollback of any open transactions. Then the databaseis shut down.ABORTNo new connections are allowed, and no new transactions are allowed to bestarted after the statement is issued. All client SQL statements currentlybeing processed are terminated, without rolling back open transactions.Users are disconnected and Oracle processes are stopped.Quest:15:-process to create new control file?Quest 16:-Difference between complete backup and Incremental backup. Quest 17:- How to switch from manual to automatic undo management?Create the new undo tablespace PSAPUNDO.2. Change or insert the four new Oracle parameters with appropriate values.3. Drop all rollback segments (except the SYSTEM rollback segment).4. Delete (or comment out) the Oracle parameter rollback_segments.5. Drop the rollback tablespace.Quest 18:-What is tablespace,segment, Extent and block??

At the finest level of granularity, Oracle stores data in data blocks (also called logical blocks, Oracle blocks, or pages). One data block corresponds to a specific number of bytes of physical database space on disk.The next level of logical database space is an extent. An extent is a specific number of contiguous data blocks allocated for storing a specific type of information.The level of logical database storage greater than an extent is called a segment. A segment is a set of extents, each of which has been allocated for a specific data structure and all of which are stored in the same tablespace. For example, each table's data is stored in its own data segment, while each index's data is stored in its own index segment. If the table or index is partitioned, each partition is stored in its own segment.Oracle allocates space for segments in units of one extent. When the existing extents of a segment are full, Oracle allocates another extent for that segment. Because extents are allocated as needed, the extents of a segment may or may not be contiguous on disk.A segment and all its extents are stored in one tablespace. Within a tablespace, a segment can include extents from more than one file; that is, the segment can span datafiles. However, each extent can contain data from only one datafileQuest:-19 What is difference between R3trans x and R3trans dR3trans d check the database connectivity through OPS$ mechanismR3trans x DB connect without accessing any SAP table Quest:-20:What is index and difference between B tree and Bitmap Indexes(Google)Quest:-21What is auto extended mode in tablespace?Quest 22:-What is shared pool, Large pool and JAVA pool?Quest 23:-What IS SGA,PMON,SMON??