DBA Interview Questions With Answer

 Can you distinguish Redo vs. Rollback vs. Undo?

    There is always some misunderstandings when referring to Redo, Rollback and Undo. They all sound like basically the same thing or at least fairly close.

    Redo: Every Oracle information source has a set of (two or more) redo log data files. The redo log records all changes created to information, such as both uncommitted and dedicated changes. In addition to the online redo records Oracle also shops database redo records. All redo records are used in restoration situations.

    Rollback: More specifically rollback sections. Rollback sections shop the information as it was before the changes were created. This is on the other hand to the redo log which is a record of the insert/update/deletes.

    Undo: Rollback sections. They both are really one in the same. Undo is saved in the undo tablespace. It is helpful in building a read reliable view of information.

    What is Secure Exterior Password Store (SEPS)?

    Through the use of SEPS you can shop security password qualifications for linking to information source by using a customer side oracle pockets, this pockets shops deciding upon qualifications. This feature presented since oracle 10g. Thus the applying concept, planned job, programs no more needed included login name and security passwords. This decreases risk because the security passwords won’t be revealed and security password management coverage is more easily required without changing program concept whenever details change.

    What are the variations between Physical/Logical stand by databases? How would you decide which one is most suitable for your environment?

    Physical stand by DB:

    – As the name, it is actually (datafiles, schema, other actual identity) same duplicate of the main information source.

    – It is synchronized with the main information source with Implement Redo to the stand by DB.

    Logical Standby DB:

    – As the name sensible information is the same as the development information source, it may be physique can be different.

    – It synchronized with main information source though SQL Implement, Redo caused by the main information source into SQL claims and then performing these SQL claims on the stand by DB.

    – We can start “physical stand by DB to “read only” and create it available to the programs customers (Only choose is permitted during this period). we can not apply redo records caused by main information source at now.

    – We do not see such issues with sensible stand by information source. We can start the information source in normal method and create it available to the customers. At the same time, we may use stored records caused by main information source.– For OLTP huge deal information source it is better to choose sensible stand by information source.

    Aware. log displaying this mistake “ORA-1109 signalled during: modify information source close”. What is the key good purpose why behind it?

    The ORA-1109 mistake just indicates that the information source is not start for company. You’ll have to start it up before you can continue.

    It may be while you are closing down the information source, somebody trying to start the information source respectively. It is failing attempt to start the information source while shut down is on the way.Wait for the a chance to actually shut down the information source and start it again for use. On the other hand you have to reboot your oracle services on windows atmosphere.

    Which factors are to be considered for creating catalog on Table? How to choose line for index?

    Creation of catalog on desk relies upon on dimension desk, number of information. If dimension desk is huge and we need only few information for choosing or in review then we need to develop catalog. There are some basic purpose of choosing line for listing like cardinality and regular utilization in where condition of choose question. Business concept is also pushing to develop catalog like main key, because establishing main key or exclusive key instantly create exclusive catalog.

    It is worth noting that development of so many indices would change the performance of DML on desk because in single deal should need to perform on various catalog sections and desk simultaneously.

    How can you management variety of datafiles in oracle database?

    The db_files parameter is a “soft restrict ” parameter that manages the most of actual OS data files that can map to an Oracle example. The maxdatafiles parameter is a different – “hard limit” parameter. When providing a “create database” control, the value specified for max data files is saved in Oracle management data files and standard value is 32. The most of information source data files can be set with the init parameter db_files.

    Regardless of the setting of this parameter, highest possible per database: 65533 (May be less on some working systems), Maximum variety of datafiles per tablespace: OS reliant = usually 1022

    You can also by Limited dimension information source prevents and by the DB_FILES initialization parameter for a particular example. Big file table spaces can contain only one data file, but that data file can have up to 4G prevents.

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