QueryDB

Answer :- http://en.wikipedia.org/wiki/Multitier_architecture#Comparison_with_the_MVC_architecture Comparison with the MVC architecture At first glance, the three tiers may seem similar to the model-view-controller (MVC) concept; however, topologically they are different. A fundamental rule in a three tier architecture is the client tier never communicates directly with the data tier; in a three-tier model all communication must pass through the middle tier. Conceptually the three-tier architecture is linear. However, the MVC architecture is triangular: the view sends updates to the controller, the controller updates the model, and the view gets updated directly from the model. From a historical perspective the three-tier architecture concept emerged in the 1990s from observations of distributed systems (e.g., web applications) where the client, middle ware and data tiers ran on physically separate platforms. Whereas MVC comes from the previous decade (by work at Xerox PARC in th...

Here's how to lock or unlock Oracle database user accounts. SQL> ALTER USER username ACCOUNT LOCK; SQL> ALTER USER username ACCOUNT UNLOCK;

Display Oracle Listener Status $ lsnrctl status LSNRCTL for Linux: Version 11.1.0.6.0 - Production on 04-APR-2009 16:27:39 Copyright (c) 1991, 2007, Oracle. All rights reserved. Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.1.2)(PORT=1521))) TNS-12541: TNS:no listener TNS-12560: TNS:protocol adapter error TNS-00511: No listener Linux Error: 111: Connection refused Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC))) TNS-12541: TNS:no listener TNS-12560: TNS:protocol adapter error TNS-00511: No listener Linux Error: 2: No such file or directory If the Oracle listener is running, you’ll get the following message. $ lsnrctl status LSNRCTL for Linux: Version 11.1.0.6.0 - Production on 04-APR-2009 16:27:02 Copyright (c) 1991, 2007, Oracle. All rights reserved. Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.1.2)(PORT=1521))) STATUS of the LISTENER ------------------------ Alias L...

[oracle@localhost ~]$ sqlplus sys as sysdba SQL*Plus: Release 11.2.0.1.0 Production on Tue Feb 15 16:09:03 2011 Copyright (c) 1982, 2009, Oracle. All rights reserved. Enter password: Connected to an idle instance. SQL> selct * from v$version SP2-0734: unknown command beginning "selct * fr..." - rest of line ignored. SQL> select * from v$version; select * from v$version * ERROR at line 1: ORA-01034: ORACLE not available Process ID: 0 Session ID: 0 Serial number: 0 SQL> startup ORA-01078: failure in processing system parameters LRM-00109: could not open parameter file '/u01/app/oracle/product/11.2.0/db_1/dbs/initDB11G.ora'

Login to the system with oracle username $ su - oracle Make sure ORACLE_SID and ORACLE_HOME are set properly as shown below. $ env | grep ORA Connect to oracle sysdba $ sqlplus '/ as sysdba' Start Oracle Database SQL> startup Shutdown shutdown