DataBase Administrator (DBA) Interview Questions and Answers
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34. What does a Control file Contain?
A Control file records the physical structure of the database. It contains the following information. Database Name Names and locations of a database’s files and redolog files. Time stamp of database creation.
35. What is difference between UNIQUE constraint and PRIMARY KEY constraint?
A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can’t contain Nulls. 47.What is Index Cluster? - A Cluster with an index on the Cluster Key 48.When does a Transaction end? - When it is committed or Rollbacked.
36. What is the effect of setting the value “ALL_ROWS” for OPTIMIZER_GOAL parameter of the ALTER SESSION command?
What are the factors that affect OPTIMIZER in choosing an Optimization approach? - Answer The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.
37. Describe what redo logs are.
Redo logs are logical and physical structures that are designed to hold all the changes made to a database and are intended to aid in the recovery of a database.
38. How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;
39. What are the different Parameter types?
Text ParametersData Parameters
40. What does coalescing a tablespace do?
Coalescing is only valid for dictionary-managed tablespaces and de-fragments space by combining neighboring free extents into large single extents.
41. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for temporary objects such as sort structures while permanent tablespaces are used to store those objects meant to be used as the true objects of the database.
42. Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
43. When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.
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