$ORACLE_BASE for installation purpose only.
oracle will use it to determine the optimal disk structure (oradata oraInventory
product etc). it's optional.
$ORACLE_HOME is usually
$ORACLE_BASE/product/
where all kinds of oracle files resides. it is required for all oracle runtime
operations and software
maitainance.
简单说,ORACLE_BASE是oracle的根目录，ORACLE_HOME是oracle产品的目录。
例如：如果装了2个版本的oracle，那么ORACLE_BASE可以是一个，但ORACLE_HOME是2个。