查看“_gc”开头的隐藏参数值：
set linesize 333
col name for a35
col description for a66
col value for a30
SELECT i.ksppinm name,
i.ksppdesc description,
CV.ksppstvl VALUE
FROM sys.x$ksppi i, sys.x$ksppcv CV
WHERE i.inst_id = USERENV ('Instance')
AND CV.inst_id = USERENV ('Instance')
AND i.indx = CV.indx
AND i.ksppinm LIKE '/_gc%' ESCAPE '/'
ORDER BY REPLACE (i.ksppinm, '_', '');
–11g RAC关闭DRM特性
alter system set "_gc_policy_time"=0 scope=spfile sid='*'; alter system set "_gc_undo_affinity"=false scope=spfile sid='*';
–10g RAC关闭DRM特性
alter system set "_gc_affinity_time"=0 scope=spfile sid='*'; alter system set "_gc_undo_affinity"=FALSE scope=spfile sid='*';
参考老熊的文章，http://www.laoxiong.net/problem-caused-by-drm.html
10g RAC可以设置另外2个动态的隐含参数，来达到从”事实上“关闭DRM的目的：
_gc_affinity_limit=250 _gc_affinity_minimum=10485760
