笔记：Memory Notification: Library Cache Object loaded into SGA
在警告日志中发现一些这样的警告信息：
Mon Nov 21 14:24:22 2011
Memory Notification: Library Cache Object loaded into SGA
Heap size 5800K exceeds notification threshold (2048K)
Details in trace file c:\oracle\product\10.2.0\admin\hy2003\udump\hy2003_ora_4372.trc
KGL object name :PCDM.BIN$C8iYfZ9TS8ORv9KUD+hrSA==$0
在网上查到：
【问题处理】Memory Notification: Library Cache Object loaded into SGA
1.问题现象
数据库日常巡检过程中，在alert日志中发现如下警告信息
……省略……
Thu Apr 15 22:06:31 2010
Memory Notification: Library Cache Object loaded into SGA
Heap size 3215K exceeds notification threshold (2048K)
KGL object name :SELECT TOWNER, TNAME, NAME, LENGTH, PRECISION, SCALE, TYPE, ISNULL, CONNAME, COLID, INTCOLID, SEGCOLID, COMMENT$, DEFAULT$, DFLTLEN, ENABLED, DEFER, FLAGS, COLPROP, ADTNAME, ADTOWNER, CHARSETID, CHARSETFORM, FSPRECISION, LFPRECISION, CHARLEN, TFLAGS, TYPESYN, COLCLASS FROM SYS.EXU10COE WHERE TOBJID = :1 ORDER BY COLCLASS
Thu Apr 15 22:06:55 2010
Memory Notification: Library Cache Object loaded into SGA
Heap size 5118K exceeds notification threshold (2048K)
Details in trace file /home/oracle/oracle/product/10.2.0/db_1/admin/orcl/udump/orcl_ora_18031.trc
KGL object name :SELECT SYS_XMLGEN(VALUE(KU$), XMLFORMAT.createFormat2('TABLE_T', '7')), KU$.OBJ_NUM FROM SYS.KU$_FHTABLE_VIEW KU$ WHERE NOT (BITAND (KU$.PROPERTY,8192)=8192) AND NOT BITAND(KU$.SCHEMA_OBJ.FLAGS,128)!=0 AND KU$.SCHEMA_OBJ.NAME=:NAME1 AND KU$.SCHEMA_OBJ.OWNER_NAME=:SCHEMA2
Fri Apr 16 05:00:07 2010
……省略……
2.问题原因
在Oracle 10.2.0.1版本数据库中隐含参数_kgl_large_heap_warning_threshold默认值是2M，该参数控制加载到内存中对象的大小，当加载的对象大于2M时，就会在alert警告文件中进行提示。2M的默认大小相对太小，因此在10.2.0.1版本中可能很容易遇到这个报错信息。该参数默认值在10.2.0.2版本中进行了调整，调整到了50M。
1）确认出现警告的数据库的版本是10.2.0.1
sys@orcl> select * from v$version;
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production
2）确认隐含参数_kgl_large_heap_warning_threshold的默认大小
sys@orcl> select a.ksppinm name,b.ksppstvl value,a.ksppdesc description
2 from x$ksppi a,x$ksppcv b
3 where a.indx = b.indx
4 and a.ksppinm = '_kgl_large_heap_warning_threshold'
5 /
NAME VALUE DESCRIPTION
--------------------------------- -------- --------------------------------------------------------------
_kgl_large_heap_warning_threshold 2097152 maximum heap size before KGL writes warnings to the alert log
sys@orcl> select 2097152/1024/1024 MB from dual;
MB
----------
2
3.问题处理方法
既然知道了问题原因，处理起来就很简单了。如果不希望在alert文件中看到这些报错，可以适当调大隐含参数“_kgl_large_heap_warning_threshold”的值，或将其设置为“0”。
1）将_kgl_large_heap_warning_threshold参数大小调整为50M
sys@orcl> alter system set "_kgl_large_heap_warning_threshold"=52428800 scope=spfile;
System altered.
2）重启数据库
OK，该问题到此已得到有效处理。
select a.ksppinm name,b.ksppstvl value,a.ksppdesc description
from x$ksppi a,x$ksppcv b
where a.indx = b.indx
and a.ksppinm = '_kgl_large_heap_warning_threshold';
NAME VALUE DESCRIPTION
----------------------- ------------------------------ -------------------------------
_kgl_large_heap_warning_threshold 2097152 maximum heap size before KGL writes warnings to the alert log
按介绍修改参数：
System altered alter system set '_kgl_large_heap_warning_threshold'=8388608 scope=spfile ;
重启数据库。
NOTE:
The default threshold in 10.2.0.1 is 2M.
So these messages could show up frequently in some application environments.
In 10.2.0.2, the threshold was increased to 50MB after regression tests, so this should be a reasonable and recommended value. If you continue to see the these warning messages in the alert log after applying 10.2.0.2 or higher, an SR may be in order to investigate if you are encountering a bug in the Shared Pool.