21⟩ What is a Segment?
A segment is a set of extents allocated for a certain logical structure.
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253 Database Administrator (DBA) Questions And Answers
22⟩ Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.
23⟩ Give the reasoning behind using an index.
Faster access to data blocks in a table.
24⟩ Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces a now rollback. The delete command, on the other hand, is a DML operation, which will produce a rollback and thus take longer to complete.
25⟩ What view would you use to determine free space in a tablespace?
DBA_FREE_SPACE
26⟩ What view would you use to look at the size of a data file?
DBA_DATA_FILES
27⟩ How do you add a data file to a tablespace?
ALTER TABLESPACE ADD DATAFILE <datafile_name> SIZE <size>
28⟩ How do you resize a data file?
ALTER DATABASE DATAFILE <datafile_name> RESIZE <new_size>;
29⟩ Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
30⟩ When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.
31⟩ 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.
32⟩ 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.
33⟩ 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.
34⟩ How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;
35⟩ 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.
36⟩ 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.
37⟩ Explain materialized views and how they are used.
Materialized views are objects that are reduced sets of information that have been summarized, grouped, or aggregated from base tables. They are typically used in data warehouse or decision support systems.
38⟩ What are the different Parameter types?
Text ParametersData Parameters
39⟩ 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.
40⟩ Where in the Oracle directory tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the event viewer
