2020. 2. 21. 14:51ㆍ카테고리 없음
Question 2 What is the difference between Oracle database and Oracle instance?Answer:Oracle database is the collection of datafiles,redologs and control files while Oracle instance is the SGA,processes in the Memory.We can have 1 or more instance serving a oracle database. In, we have one set of datafiles,control file and while instance on one ore more boxes accesses the same databaseQuestion 3 What is a Tablespace?Answer: Oracle use Tablespace for logical data Storage.
Physically, data will get stored in Datafiles. Datafiles will be connected to tablespace. A tablespace can have multiple datafiles.
A tablespace can have objects from different schema’s and a schema can have multiple. Database creates “SYSTEM tablespace” by default during database creation.
It contains read only data dictionary tables which contains the information about the database.Question 4 What are Datafiles?Answer:The datafiles contain all the database data. The data of logical database structures, such as and, is physically stored in the datafiles allocated for a database.Question 5 what is Control Files?Answer:Every Oracle database has a control file.
A control file contains entries that specify the physical structure of the database such as Database name and the Names and locations of datafiles and redo log files.Question 6 What is Redo Log Files?Answer The primary function of the redo log is to record all changes made to data. If a failure prevents modified data from being permanently written to the datafiles, then the changes can be obtained from the redo log, so work is never lost.Question 7 What is Archive Log Files?Answer:Oracle automatically when the database is in ARCHIVELOG mode. This prevents oracle from overwriting the redo log files before they have been safely archived to another location.Question 8 What is Parameter Files (initSID.ora)Answer:Parameter files contain a list of configuration parameters for that instance and database.Question 9 What is schema?Answer:A and its associated data including tables, indexes, clusters,procedures, functions, triggers,packages and database links is known as Oracle schema.
System, SCOTT etc are default schema’s. We can create a new Schema/User. But we can’t drop default database schema’s.Question 10 What is data blocks?Answer:Data Blocks are the base unit of logical database space. Sqlplus / as sysdbashutdown abortChange Init.ora file to remove the lost controlfile or copy the existing controlfile to that locationstartup the databaseCheck below link for all the useful scenario for recoveryQuestion 26. How do you if you lost all of the controlfile in the database?Answera. Shutdown Instance (abort)b.
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If the control-file backup is available,then restore it from backup or if you have got the controlfile information in trace using alter database backup controlfile to tracec. Once the controlfile is created, recover database using backup controlfile.
You will need to apply the redo logs to complete the recoveryd, alter database open resetlogs;We can avoid the resetlogs by using the steps below1. After the database is mounted with restore of controlfile from backup,create a trace of the controlfile using the command belowalter database backup controlfile to trace;2. Now take out the create controlfile statement from the trace. Choose the NORESETLOG portion3.
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Recreate the controlfile using the above portion.4. Do recover database5. Alter database openCheck below link for all the useful scenario for recoveryQuestion 27. What is flashback database?Answer:It is New feature in Oracle database post 10.1 onwards.
It Uses past block images to back out changes to a. As the name suggest, we can use this flashback database in previous timea.During normal database operation, Oracle occasionally logs past block images in flashback logsb.Flashback logs are written sequentially not archivedc. Oracle automatically creates, resizes and deletes flashback logs in the flash recovery aread. DBA should be aware of flashback logs to monitor performance,to decide how much space to allocate to flash recovery areae.