待完善…
The output may look like,
Operation | Options | Object Name | Cost | Cardinality | Bytes
Operation, Options: 数据库在这一步采取的操作及其使用的参数. 请参考
所有操作的集合
Object Name: Name of the table or index.
Cost: a function of the CPU_COST and IO_COST. 它是无量纲的，仅用于各步操作的代价比较
Cardinality: the number of rows accessed by the operation
Bytes: the number of bytes accessed by the operation
更多：
http://download.oracle.com/docs/cd/E11882_01/server.112/e10821/ex_plan.htm#i18300