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Computer Interview Questions Answers

Oracle Interview Questions Answers

Question - 121 : - What is the mechanism provided by ORACLE for table replication ?

Answer - 121 : - Snapshots and SNAPSHOT LOGs

Question - 122 : - What are the types of synonyms?

Answer - 122 : - There are two types of synonyms private and public.

Question - 123 : - How are extents allocated to a segment? (for DBA)

Answer - 123 : - Oracle8 and above rounds off extents to a multiple of 5 blocks when more than 5 blocks are requested. If one requests 16K or 2 blocks (assuming a 8K block size), Oracle doesn't round it up to 5 blocks, but it allocates 2 blocks or 16K as requested. If one asks for 8 blocks, Oracle will round it up to 10 blocks. Space allocation also depends upon the size of contiguous free space available. If one asks for 8 blocks and Oracle finds a contiguous free space that is exactly 8 blocks, it would give it you. If it were 9 blocks, Oracle would also give it to you. Clearly Oracle doesn't always round extents to a multiple of 5 blocks. The exception to this rule is locally managed tablespaces. If a tablespace is created with local extent management and the extent size is 64K, then Oracle allocates 64K or 8 blocks assuming 8K-block size. Oracle doesn't round it up to the multiple of 5 when a tablespace is locally managed.

Question - 124 : - How does one do off-line database backups?

Answer - 124 : - Shut down the database from sqlplus or server manager. Backup all files to secondary storage (eg. tapes). Ensure that you backup all data files, all control files and all log files. When completed, restart your database. Do the following queries to get a list of all files that needs to be backed up: select name from sys.v_$datafile; select member from sys.v_$logfile; select name from sys.v_$controlfile; Sometimes Oracle takes forever to shutdown with the "immediate" option. As workaround to this problem, shutdown using these commands: alter system checkpoint; shutdown abort startup restrict shutdown immediate Note that if you database is in ARCHIVELOG mode, one can still use archived log files to roll forward from an off-line backup. If you cannot take your database down for a cold (off-line) backup at a convenient time, switch your database into ARCHIVELOG mode and perform hot (on-line) backups.

Question - 125 : - What is difference between UNIQUE constraint and PRIMARY KEY constraint ?

Answer - 125 : - A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.

Question - 126 : - Explain the relationship among database, tablespace and data file ?

Answer - 126 : - Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.

Question - 127 : - What are Most Common types of Complex master-detail relationships?

Answer - 127 : - There are three most common types of complex master-detail relationships: master with dependent details master with independent details detail with two masters

Question - 128 : - What are the built-ins used for finding Object ID function?

Answer - 128 : - FIND_GROUP(function) FIND_COLUMN(function)

Question - 129 : - Define Transaction ?

Answer - 129 : - A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.

Question - 130 : - What is system.coordination_operation?

Answer - 130 : - It represents the coordination causing event that occur on the master block in master-detail relation.

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