V$SYS_TIME_MODEL
V$SESS_TIME_MODEL

DB Time

Amount of elapsed time (in microseconds) spent performing Database user-level calls. This does not include the elapsed time spent on instance background processes such as PMON.

所有 foreground session 花费在 database 调用上的总和时间

包括 CPU时间( DB CPU)、IO Time、和其他一系列非空闲等待时间，别忘了cpu on queue time

公式：DB TIME= DB CPU + Non-Idle Wait + Wait on CPU queue

DB CPU

Amount of CPU time (in microseconds) spent on database user-level calls. This does not include the CPU time spent on instance background processes such as PMON.

数据库在运行时消耗的CPU的情况,不包含数据库进程在等待CPU的时间。

1) background elapsed time2) background cpu time3) RMAN cpu time (backup/restore)
1) DB time2) DB CPU2) connection management call elapsed time2) sequence load elapsed time2) sql execute elapsed time2) parse time elapsed3) hard parse elapsed time4) hard parse (sharing criteria) elapsed time5) hard parse (bind mismatch) elapsed time3) failed parse elapsed time4) failed parse (out of shared memory) elapsed time2) PL/SQL execution elapsed time2) inbound PL/SQL rpc elapsed time2) PL/SQL compilation elapsed time2) Java execution elapsed time2) repeated bind elapsed time

如果 DB Time 和 DB CPU 相差不大，说明等待事件较少或不太严重，或者SQL执行较慢。
如果 DB Time 远远大于 DB CPU，通常情况下表明等待比较严重，即使SQL执行很快，但是大部分处于等待状态。

参考:
https://docs.oracle.com/cd/E11882_01/server.112/e40402/dynviews_3088.htm#REFRN30346
https://docs.oracle.com/cd/E11882_01/server.112/e40402/dynviews_3015.htm#REFRN30340