Oracle Database Commonly Used Commands

ps -x

cat /etc/oratab

export ORACLE_SID=

export ORACLE_HOME=

export PATH=$ORACLE_HOME/bin:$PATH:$HOME/bin:.

sqlplus / as sysdba

startup

select name,open_mode from v$database;

lsnrctl start/status


show parameter spfile

results in a clear format 
========================
col name <column_name> 256
set lines 256
set trimout on
set space 1
set tab off