OWI监控和收集方法——利用PL/SQL过程进行性能数据采样（2）

用数据库注销触发器方法收集历史性能数据还缺少SQL语句的存储。如果能够以规则的间隔对每一个连接到实例的前台进程进行采样，并将数据写入存储表中，则将拥有每一个进程自开始至完成期间在数据库中所做事情的历史记录。我们称这种性能数据收集器为DC。该任务的最佳数据源是V$SESSION_WAIT视图。DBA有选择高采样频率的倾向，但通常一分钟比较合适。若将该采样与前面讨论的数据库注销触发器相补充，则既可获得汇总等待事件，又可获得所有会话的详细的一分钟接一分钟的等待事件和SQL语句。

创建表的脚本：

create table session_snap_history
(
  sid             NUMBER,
  serial#         NUMBER,
  seq#            NUMBER,
  event           VARCHAR2(64),
  logon_time      DATE,
  sql_hash_value  NUMBER,
  sql_id          VARCHAR2(13),
  p1text          VARCHAR2(64),
  p1              NUMBER,
  p1raw           RAW(8),
  p2text          VARCHAR2(64),
  p2              NUMBER,
  p2raw           RAW(8),
  p3text          VARCHAR2(64),
  p3              NUMBER,
  p3raw           RAW(8),
  wait_time       NUMBER,
  seconds_in_wait NUMBER,
  state           VARCHAR2(19),
  username        VARCHAR2(30),
  osuser          VARCHAR2(30),
  paddr           RAW(4),
  process         VARCHAR2(24),
  saddr           RAW(4),
  module          VARCHAR2(48),
  row_wait_obj#   NUMBER,
  row_wait_file#  NUMBER,
  row_wait_block# NUMBER,
  row_wait_row#   NUMBER,
  target_obj      VARCHAR2(2000),
  sql_text        BLOB,
  disk_reads      NUMBER,
  buffer_gets     NUMBER
) tablespace users;

采样存过：

  /*
  * Remark：This is an incomplete procedure.
  */
  create or replace procedure DC is
  cursor current_event is
    select s.SID,
           s.SERIAL#,
           s.SEQ#,
           s.EVENT,
           s.LOGON_TIME,
           s.SQL_HASH_VALUE,
           s.SQL_ID,
           P1TEXT,
           s.P1,
           s.P1RAW,
           s.P2TEXT,
           s.P2,
           s.P2RAW,
           s.P3TEXT,
           s.P3,
           s.P3RAW,
           s.WAIT_TIME,
           s.SECONDS_IN_WAIT,
           s.STATE,
           s.USERNAME,
           s.OSUSER,
           s.PADDR,
           s.PROCESS,
           s.SADDR,
           s.MODULE,
           s.ROW_WAIT_OBJ#,
           s.ROW_WAIT_FILE#,
           s.ROW_WAIT_BLOCK#,
           s.ROW_WAIT_ROW#
      from sys.v$session s
     where s.USERNAME is not null
       and s.TYPE <> 'BACKGROUND'
       and s.EVENT in ('db file sequential read', --想要采样的event可以添加
                       'db file scattered read',
                       'latch free',
                       'direct path read',
                       'direct path write',
                       'library cache pin',
                       'library cache load lock',
                       'buffer busy waits',
                       'free buffer waits');
  current_event_record current_event%rowtype;
  v_target_obj         varchar2(2000); --属于等待事件的数据库对象名称
  v_sql_text           blob; --SQL语句
  v_disk_reads         number; --所有子游标运行这条语句导致的读磁盘次数
  v_buffer_gets        number; --所有子游标运行这条语句导致的读内存次数
  v_sql_hash_value     varchar2(200);
  v_sql_id             varchar2(200);
begin
  open current_event;

  loop
    fetch current_event
      into current_event_record;
    exit when current_event%notfound;
  
    /*if后面加elsif来分别判断每个event，取出v_target_obj。*/
    if current_event_record.event = 'db file sequential read' or
       current_event_record.event = 'db file scattered read' then
    
      v_sql_hash_value := current_event_record.sql_hash_value;
      v_sql_id         := current_event_record.sql_id;
    
      select 'segment_name:' || t.segment_name || ';' || 'partition_name:' ||
             t.partition_name
        into v_target_obj
        from dba_extents t
       where current_event_record.p2 between t.BLOCK_ID and
             (t.BLOCK_ID + t.BLOCKS - 1)
         and t.FILE_ID = current_event_record.p1;
    
    end if;
  
    select t.SQL_TEXT --取出SQL语句
      into v_sql_text
      from v$sqltext t
     where t.HASH_VALUE = v_sql_hash_value;
  
    select v_disk_reads, v_buffer_gets --取出读磁盘次数和读内存次数
      into v_disk_reads, v_buffer_gets
      from (select t.SQL_ID,
                   sum(t.DISK_READS) DISK_READS,
                   sum(t.BUFFER_GETS) BUFFER_GETS
              from v$sqlarea t
             group by t.SQL_ID)
     where SQL_ID = v_sql_id;
  
    insert into u1.session_snap_history --save
      (sid,
       serial#,
       seq#,
       event,
       logon_time,
       sql_hash_value,
       sql_id,
       p1text,
       p1,
       p1raw,
       p2text,
       p2,
       p2raw,
       p3text,
       p3,
       p3raw,
       wait_time,
       seconds_in_wait,
       state,
       username,
       osuser,
       paddr,
       process,
       saddr,
       module,
       row_wait_obj#,
       row_wait_file#,
       row_wait_block#,
       row_wait_row#,
       target_obj,
       sql_text,
       disk_reads,
       buffer_gets)
    values
      (current_event_record.sid,
       current_event_record.serial#,
       current_event_record.seq#,
       current_event_record.event,
       current_event_record.logon_time,
       current_event_record.sql_hash_value,
       current_event_record.sql_id,
       current_event_record.p1text,
       current_event_record.p1,
       current_event_record.p1raw,
       current_event_record.p2text,
       current_event_record.p2,
       current_event_record.p2raw,
       current_event_record.p3text,
       current_event_record.p3,
       current_event_record.p3raw,
       current_event_record.wait_time,
       current_event_record.seconds_in_wait,
       current_event_record.state,
       current_event_record.username,
       current_event_record.osuser,
       current_event_record.paddr,
       current_event_record.process,
       current_event_record.saddr,
       current_event_record.module,
       current_event_record.row_wait_obj#,
       current_event_record.row_wait_file#,
       current_event_record.row_wait_block#,
       current_event_record.row_wait_row#,
       v_target_obj,
       v_sql_text,
       v_disk_reads,
       v_buffer_gets);
    commit;
  
  end loop;

  close current_event;
end;
/

用操作系统的crontab 或者 数据库的job、scheduler来调用这个存过就可以采样数据了。