根据dba_hist_osstat统计CPU占用情况

在11g里面，视图dba_hist_osstat用来记录OS级别的time时间指标。视图dba_hist_osstat_name显示了相关的指标名称。

SYS@134.32.114.1:/dzgddb> select * from DBA_HIST_OSSTAT_NAME;

           DBID         STAT_ID STAT_NAME
--------------- --------------- ----------------------------------------------------------------
                     NUM_CPUS
                     IDLE_TIME
                     BUSY_TIME
                     USER_TIME
                     SYS_TIME
                     IOWAIT_TIME
                     NICE_TIME
                    RSRC_MGR_CPU_WAIT_TIME
                    LOAD
                    NUM_CPU_CORES
                    NUM_CPU_SOCKETS
                  PHYSICAL_MEMORY_BYTES
                  VM_IN_BYTES
                  VM_OUT_BYTES
                  TCP_SEND_SIZE_MIN
                  TCP_SEND_SIZE_DEFAULT
                  TCP_SEND_SIZE_MAX
                  TCP_RECEIVE_SIZE_MIN
                  TCP_RECEIVE_SIZE_DEFAULT
                  TCP_RECEIVE_SIZE_MAX
                  GLOBAL_SEND_SIZE_MAX
                  GLOBAL_RECEIVE_SIZE_MAX

 rows selected.

如上，nmu_cpu_cores是指cpu核心数，本例是32；num_cpus是指cpu核心线程数，本例是64；num_cpu_sockets是指cpu路数，也指cpu主板数，本例是4。

关键的计算公式是：

%User = USER_TIME/ (BUSY_TIME+IDLE_TIME)*
%Sys = SYS_TIME/ (BUSY_TIME+IDLE_TIME)*
%Idle = IDLE_TIME/ (BUSY_TIME+IDLE_TIME)*100
BUSY_TIME + IDLE_TIME = ELAPSED_TIME * CPU_COUNT

鉴于报表习惯，将关键指标%Idle换算为%CPU，则：

%CPU = BUSY_TIME/ (BUSY_TIME+IDLE_TIME)*100

顺带记录一下，LOAD指标记录的是snap_id起始点的OS Load值，对应AWR报告的Load Average End & Load Average Begin。

以下是最终的SQL：根据dba_hist_osstat统计CPU占用情况，顺带附上另外几个关键指标

SELECT sn.instance_number,
       sn.snap_id,
       to_char(sn.end_interval_time, 'YYYY-MM-DD HH24:MI') AS snaptime,
       newread.value - oldread.value "physical reads",
       newwrite.value - oldwrite.value "physical writes",
       round((newdbtime.value - olddbtime.value) /  / , ) "DB time(min)",
       round((newbusy.value - oldbusy.value) /
             ((newidle.value - oldidle.value) +
             (newbusy.value - oldbusy.value)) * ,
             ) "CPU(%)"
  FROM dba_hist_sysstat        oldread,
       dba_hist_sysstat        newread,
       dba_hist_sysstat        oldwrite,
       dba_hist_sysstat        newwrite,
       dba_hist_sys_time_model olddbtime,
       dba_hist_sys_time_model newdbtime,
       dba_hist_osstat         oldidle,
       dba_hist_osstat         newidle,
       dba_hist_osstat         oldbusy,
       dba_hist_osstat         newbusy,
       dba_hist_snapshot       sn
 WHERE newread.stat_name = 'physical reads'
   AND oldread.stat_name = 'physical reads'
   AND newread.snap_id = sn.snap_id
   AND oldread.snap_id = sn.snap_id -
   AND newread.instance_number = sn.instance_number
   AND oldread.instance_number = sn.instance_number
   AND newread.dbid = sn.dbid
   AND oldread.dbid = sn.dbid
   AND newwrite.stat_name = 'physical writes'
   AND oldwrite.stat_name = 'physical writes'
   AND newwrite.snap_id = sn.snap_id
   AND oldwrite.snap_id = sn.snap_id -
   AND newwrite.instance_number = sn.instance_number
   AND oldwrite.instance_number = sn.instance_number
   AND newwrite.dbid = sn.dbid
   AND oldwrite.dbid = sn.dbid
   AND newdbtime.stat_name = 'DB time'
   AND olddbtime.stat_name = 'DB time'
   AND newdbtime.snap_id = sn.snap_id
   AND olddbtime.snap_id = sn.snap_id -
   AND newdbtime.instance_number = sn.instance_number
   AND olddbtime.instance_number = sn.instance_number
   AND newdbtime.dbid = sn.dbid
   AND olddbtime.dbid = sn.dbid
   AND newidle.stat_name = 'IDLE_TIME'
   AND oldidle.stat_name = 'IDLE_TIME'
   AND newidle.snap_id = sn.snap_id
   AND oldidle.snap_id = sn.snap_id -
   AND newidle.instance_number = sn.instance_number
   AND oldidle.instance_number = sn.instance_number
   AND newidle.dbid = sn.dbid
   AND oldidle.dbid = sn.dbid
   AND newbusy.stat_name = 'BUSY_TIME'
   AND oldbusy.stat_name = 'BUSY_TIME'
   AND newbusy.snap_id = sn.snap_id
   AND oldbusy.snap_id = sn.snap_id -
   AND newbusy.instance_number = sn.instance_number
   AND oldbusy.instance_number = sn.instance_number
   AND newbusy.dbid = sn.dbid
   AND oldbusy.dbid = sn.dbid
 ORDER BY sn.instance_number, sn.snap_id;