Getting tablespace Size

SELECT tablespace_name,
       SUM (bytes) / 1024 / 1024 current_size,
       autoextensible,
       SUM (maxbytes) / 1024 / 1024 max_size
FROM dba_data_files
WHERE tablespace_name like '%'
GROUP BY tablespace_name, autoextensible
ORDER BY 1

bash : search and replace from previous command

tar -cvf sandeep.tar sandeep/

!!:gs/sandeep/singhal will mean

tar -cvf singhal.tar singhal/

:gs is for global search and replace

bash - last argument of the previous command (nth argument)

• Get the last argument of the previous command : !!$
• Get the first argumnet of the previous command : !!^
• Get the 1st argument of the previous command : !!1
• Get the nth argument of the previous command : !!n

Examples : 

$> ls :!!$  (or !$) 

$> ls :!!^

$> ls :!!2

$> ls :!!n

Trigger GC in eclipse.

This is a handy for eclipse which lets you to trigger gc in the eclipse instead of waiting for the jvm to schedule the GC .

Go to Window->Preferences->General, mark Show Heap status check box.
The current Heap usage with icon for "Run Garbage Collector" will appear at the bottom right.

It helps a lot in eclipse performance.

I find it pretty handy especially because I do not shutdown eclipse often.

Two things I love about opera

1. You can type windows specific path on the browser bar and it will covert it to "forward slashes" when you are browsing directory like strucure on a browser

2. The quick search box : The cursor remains at the same place if you go to a different window by "ALT-TAB". This in firefox changes to select the entire text already typed in the search box. Hence you cannot start typing straight away, since that will erase the already entered text. 

Common sqlplus commands

ACCEPT - Get input from the user 
DEFINE - Declare a variable (short: DEF) 
DESCRIBE - Lists the attributes of tables and other objects (short: DESC) 
EDIT - Places you in an editor so you can edit a SQL command (short: ED) 
EXIT or QUIT - Disconnect from the database and terminate SQL*Plus 
GET - Retrieves a SQL file and places it into the SQL buffer 
HOST - Issue an operating system command (short: !) 
LIST - Displays the last command executed/ command in the SQL buffer (short: L) 
PROMPT - Display a text string on the screen. Eg prompt Hello World!!! 
RUN - List and Run the command stored in the SQL buffer (short: /) 
SAVE - Saves command in the SQL buffer to a file. Eg "save x" will create a script file called x.sql 
SET - Modify the SQL*Plus environment eg. SET PAGESIZE 23 
SHOW - Show environment settings (short: SHO). Eg SHOW ALL, SHO PAGESIZE etc. 
SPOOL - Send output to a file. Eg "spool x" will save STDOUT to a file called x.lst 
START - Run a SQL script file (short: @)

source :

http://www.orafaq.com/wiki/SQL*Plus_FAQ

Oracle - Default Location for data files

To get the existing location

sql > show parameter db_create;

To set a new location

sql> alter system set db_create_file_dest='/home/ssinghal/oradata';