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59. What are the Limitations of a CHECK Constraint ?
The condition must be a Boolean expression evaluated using the
values in the row being inserted or updated and can't contain
subqueries, sequence, the SYSDATE,UID,USER or USERENV SQL functions,
or the pseudo columns LEVEL or ROWNUM.
60. What is the maximum number of CHECK constraints that can be
defined on a column ?
No Limit.
SYSTEM ARCHITECTURE :
61. What constitute an ORACLE Instance ?
SGA and ORACLE background processes constitute an ORACLE instance.
(or) Combination of memory structure and background process.
62. What is SGA ?
The System Global Area (SGA) is a shared memory region allocated by
ORACLE that contains data and control information for one ORACLE
instance.
63. What are the components of SGA ?
Database buffers, Redo Log Buffer the Shared Pool and Cursors.
64. What do Database Buffers contain ?
Database buffers store the most recently used blocks of database
data. It can also contain modified data that has not yet been
permanently written to disk.
65. What do Redo Log Buffers contain ?
Redo Log Buffer stores redo entries a log of changes made to the
database.
66. What is Shared Pool ?
Shared Pool is a portion of the SGA that contains shared memory
constructs such as shared SQL areas.
67. What is Shared SQL Area ?
A Shared SQL area is required to process every unique SQL
statement submitted to a database and contains information such as the
parse tree and execution plan for the corresponding statement.
68. What is Cursor ?
A Cursor is a handle ( a name or pointer) for the memory associated
with a specific statement.
69. What is PGA ?
Program Global Area (PGA) is a memory buffer that contains data and
control information for a server process.
70. What is User Process ?
A user process is created and maintained to execute the software code
of an application program. It is a shadow process created
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