查看Oracle数据库服务器使用情况

查看Oracle数据库服务性能一般从内存使用情况、IO读写速度、网络传输速率进行排查。

 

一、Oracle 内存结构
SGA(System Global Area)：由所有服务进程和后台进程共享；
PGA(Program Global Area)：由每个服务进程、后台进程专有；每个进程都有一个PGA。

二、SGA
包含实例的数据和控制信息，包含如下内存结构：
1）Database buffer cache：缓存了从磁盘上检索的数据块。
2）Redo log buffer：缓存了写到磁盘之前的重做信息。
3）Shared pool：缓存了各用户间可共享的各种结构。
4）Large pool：一个可选的区域，用来缓存大的I/O请求，以支持并行查询、共享服务器模式以及某些备份操作。
5）Java pool：保存java虚拟机中特定会话的数据与java代码。
6）Streams pool：由Oracle streams使用。
7）Keep buffer cache：保存buffer cache中存储的数据，使其尽时间可能长。
8）Recycle buffer cache：保存buffer cache中即将过期的数据。
9）nK block size buffer：为与数据库默认数据块大小不同的数据块提供缓存。用来支持表空间传输。

database buffer cache, shared pool, large pool, streams pool与Java pool根据当前数据库状态，自动调整；
keep buffer cache,recycle buffer cache,nK block size buffer可以在不关闭实例情况下，动态修改。

三、PGA
每个服务进程私有的内存区域，包含如下结构：
1）Private SQL area：包含绑定信息、运行时的内存结构。每个发出sql语句的会话，都有一个private SQL area（私有SQL区）
2）Session memory：为保存会话中的变量以及其他与会话相关的信息，而分配的内存区。

查看SGA与PGA的分配情况以及使用情况sql语句如下：

select  name,
       total,
       round(total - free, 2) used,
       round(free, 2) free,
       round((total - free) / total * 100, 2) pctused  from(select 'SGA' name,
                                                                    (select sum(value / 1024 / 1024)
                                                                       from v$sga) total,
                                                                    (select sum(bytes / 1024 / 1024)
                                                                       from v$sgastat
                                                                      where name =
                                                                            'free memory') free
                                                               from dual)

union
select name,total,round(used,2)used,round(total-used,2)free,round(used/total*100,2)pctused from(
select 'PGA' name,(select value/1024/1024 total from v$pgastat where name='aggregate PGA target parameter')total,
(select value/1024/1024 used from v$pgastat where name='total PGA allocated')used from dual)

union
select name,round(total,2) total,round((total-free),2) used,round(free,2) free,round((total-free)/total*100,2) pctused from (
select 'Shared pool' name,(select sum(bytes/1024/1024) from v$sgastat where pool='shared pool')total,
(select bytes/1024/1024 from v$sgastat where name='free memory' and pool='shared pool') free from dual)

union
select name,
       round(total, 2) total,
       round(total - free, 2) used,
       round(free, 2) free,
       round((total - free) / total, 2) pctused
  from (select 'Default pool' name,
               (select a.cnum_repl *
                       (select value
                          from v$parameter
                         where name = 'db_block_size') / 1024 / 1024 total
                  from x$kcbwds a, v$buffer_pool p
                 where a.set_id = p.LO_SETID
                   and p.name = 'DEFAULT'
                   and p.block_size =
                       (select value
                          from v$parameter
                         where name = 'db_block_size')) total,
               (select a.anum_repl *
                       (select value
                          from v$parameter
                         where name = 'db_block_size') / 1024 / 1024 free
                  from x$kcbwds a, v$buffer_pool p
                 where a.set_id = p.LO_SETID
                   and p.name = 'DEFAULT'
                   and p.block_size =
                       (select value
                          from v$parameter
                         where name = 'db_block_size')) free
          from dual)
union
select name,nvl(round(total,2),0)total,nvl(round(total-free,2),0) used,nvl(round(free,2),0) free,nvl(round((total-free)/total,2),0) pctused from (
select 'KEEP pool' name,(select a.cnum_repl*(select value from v$parameter where name='db_block_size')/1024/1024 total from x$kcbwds a, v$buffer_pool p
where a.set_id=p.LO_SETID and p.name='KEEP' and p.block_size=(select value from v$parameter where name='db_block_size')) total,
(select a.anum_repl*(select value from v$parameter where name='db_block_size')/1024/1024 free from x$kcbwds a, v$buffer_pool p where a.set_id=p.LO_SETID and p.name='KEEP' and p.block_size=(select value from v$parameter where name='db_block_size')) free from dual)

union
select name,nvl(round(total,2),0)total,nvl(round(total-free,2),0) used,nvl(round(free,2),0) free,nvl(round((total-free)/total,2),0) pctused from (
select 'RECYCLE pool' name,( select a.cnum_repl*(select value from v$parameter where name='db_block_size')/1024/1024 total from x$kcbwds a, v$buffer_pool p
where a.set_id=p.LO_SETID and p.name='RECYCLE' and p.block_size=(select value from v$parameter where name='db_block_size')) total,(select a.anum_repl*(select value from v$parameter where name='db_block_size')/1024/1024 free from x$kcbwds a, v$buffer_pool p where a.set_id=p.LO_SETID and p.name='RECYCLE' and p.block_size=(select value from v$parameter where name='db_block_size')) free from dual)
union
select name,nvl(round(total,2),0)total,nvl(round(total-free,2),0) used,nvl(round(free,2),0) free,nvl(round((total-free)/total,2),0) pctused from(
select 'DEFAULT 16K buffer cache' name,(select a.cnum_repl*16/1024 total from x$kcbwds a, v$buffer_pool p where a.set_id=p.LO_SETID and p.name='DEFAULT' and p.block_size=16384) total,(select a.anum_repl*16/1024 free from x$kcbwds a, v$buffer_pool p where a.set_id=p.LO_SETID and p.name='DEFAULT' and p.block_size=16384) free from dual)
union
select name,nvl(round(total,2),0)total,nvl(round(total-free,2),0) used,nvl(round(free,2),0) free,nvl(round((total-free)/total,2),0) pctused from(
select 'DEFAULT 32K buffer cache' name,(select a.cnum_repl*32/1024 total from x$kcbwds a, v$buffer_pool p
where a.set_id=p.LO_SETID and p.name='DEFAULT' and p.block_size=32768) total,
(select a.anum_repl*32/1024 free from x$kcbwds a, v$buffer_pool p
where a.set_id=p.LO_SETID and p.name='DEFAULT' and p.block_size=32768) free from dual)
union
select name,total,total-free used,free, (total-free)/total*100 pctused from (
select 'Java Pool' name,(select sum(bytes/1024/1024) total from v$sgastat where pool='java pool' group by pool)total,
( select bytes/1024/1024 free from v$sgastat where pool='java pool' and name='free memory')free from dual)
union
select name,Round(total,2),round(total-free,2) used,round(free,2) free, round((total-free)/total*100,2) pctused from (
select 'Large Pool' name,(select sum(bytes/1024/1024) total from v$sgastat where pool='large pool' group by pool)total,
( select bytes/1024/1024 free from v$sgastat where pool='large pool' and name='free memory')free from dual)
order by pctused desc;
查询结果入下图