Question

我需要监视Oracle 12c上的CPU消耗，为此，我正在使用以下代码：

SELECT
            *
        FROM
            (
                SELECT
                    username,
                    sid,
                    round( (cpu_usage / (
                        SELECT
                            SUM(value) total_cpu_usage
                        FROM
                            v$sesstat t
                            INNER JOIN v$session s ON(t.sid = s.sid)
                            INNER JOIN v$statname n ON(t.statistic# = n.statistic#)
                        WHERE
                            n.name LIKE '%CPU used by this session%'
                            AND   nvl(s.sql_exec_start,s.prev_exec_start) >= SYSDATE - 1 / 24
                            AND   s.status = 'ACTIVE'
                    ) ) * 100,2) cpu_usage_per_cent,
                    module_info,
                    client_info,
                    machine
                FROM
                    (
                        SELECT
                            nvl(s.username,'Oracle Internal Proc.') username,
                            s.sid,
                            t.value cpu_usage,
                            nvl(s.module,s.program) module_info,
                            DECODE(s.osuser,'oracle',s.client_info,s.osuser) client_info,
                            s.machine
                        FROM
                            v$sesstat t
                            INNER JOIN v$session s ON ( t.sid = s.sid )
                            INNER JOIN v$statname n ON ( t.statistic# = n.statistic# )
                        WHERE
                            n.name LIKE '%CPU used by this session%'
                            AND   nvl(s.sql_exec_start,s.prev_exec_start) >= SYSDATE - 1 / 24
                            AND   s.status = 'ACTIVE'
                    ) s1
            )
        WHERE
            cpu_usage_per_cent > 0;

到目前为止还不错，但是SUM（CPU_USAGE_PER_CENT）有时会超过100％。而且，有时，单个连接的连接数超过100％。

有人可以解释为什么吗？我希望SUM（CPU_USAGE_PER_CENT）（很少）为100％，并且对于单个连接永远不会超过100％。

非常感谢。

Answer 1

似乎我的问题是由于ROUND操作引起的：

round( (cpu_usage / (
                        SELECT
                            SUM(value) total_cpu_usage
                        FROM
                            v$sesstat t
                            INNER JOIN v$session s ON(t.sid = s.sid)
                            INNER JOIN v$statname n ON(t.statistic# = n.statistic#)
                        WHERE
                            n.name LIKE '%CPU used by this session%'
                            AND   nvl(s.sql_exec_start,s.prev_exec_start) >= SYSDATE - 1 / 24
                            AND   s.status = 'ACTIVE'
                    ) ) * 100,2)

“ cpu_usage”和“ SUM（value）”之间的除法运算的2个部分生成2个不同的统计值。

我将所有SELECT语句替换为：

WITH main_select AS (
    SELECT
        nvl(s.username,'Oracle Internal Proc.') username,
        s.sid,
        t.value cpu_usage,
        nvl(s.module,s.program) module_info,
        DECODE(s.osuser,'oracle',s.client_info,s.osuser) client_info,
        s.machine
    FROM
        v$sesstat t
        INNER JOIN v$session s ON ( t.sid = s.sid )
        INNER JOIN v$statname n ON ( t.statistic# = n.statistic# )
    WHERE
        n.name LIKE '%CPU used by this session%'
        AND   nvl(s.sql_exec_start,s.prev_exec_start) >= SYSDATE - 1 / 24
        AND   s.status = 'ACTIVE'
),sum_select AS (
    SELECT
        SUM(cpu_usage) suma
    FROM
        main_select
) SELECT
    username,
    sid,
    round( (main_select.cpu_usage / suma) * 100,2) cpu_usage,
    module_info,
    client_info,
    machine
  FROM
    main_select,
    sum_select
  WHERE
    round( (main_select.cpu_usage / suma) * 100,2) > 0;

这样，统计视图将仅被查询一次，并且在所有操作中将具有相同的值。

Oracle CPU使用率超过100％

1 个答案: