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环境：
OS：AIX Version 6.1
Oracle : 10.2.0.5 rac（节点rac2）
一、问题描述
晚上22:40 收到一条短信，数据库挂了，立马连上数据库，在日志里面发现:
从日志里面看问题很明显：是由于ora04031导致数据库重启。
二、分析与解决问题思路:
ora04031错误导致后台进程LCK0挂了，进而导致数据库重启：
查看当前数据库相关参数:
查看awr:
这里可以看出shared pool size 是8G ，buffer cache有 160G，有7个子池
查看dump文件/oracle/product/admin/oss139/bdump/oss1392_lck0_6685174.trc
Memory Utilization of Subpool 1
================================
Allocation Name Size
_________________________ __________
"free memory " 19127320 19M
Memory Utilization of Subpool 2
================================
Allocation Name Size
_________________________ __________
"free memory " 131103400 130M
Memory Utilization of Subpool 3
================================
Allocation Name Size
_________________________ __________
"free memory " 19409776 19M
Memory Utilization of Subpool 4
================================
Allocation Name Size
_________________________ __________
"free memory " 19172224 19M
emory Utilization of Subpool 5
================================
Allocation Name Size
_________________________ __________
"free memory " 18623928 18M
Memory Utilization of Subpool 6
================================
Allocation Name Size
_________________________ __________
"free memory " 18026416 18M
Memory Utilization of Subpool 7
================================
Allocation Name Size
_________________________ __________
"free memory " 12162296 12M
相比前一天总free memory下降到只有200多M，，对应的gcs resources,gcs shadows却占用了5G多空间，gcs resources和gcs shadow资源均是Oracle RAC中特有的全局缓存服务资源，这些资源负责处理RAC中的全局buffer cache。
然后查询shared_pool当前的剩余内存:
只有16M了，也就是昨天发生ora 04031并不是偶然。
在metalink搜索gcs resource:
Gcs 这两位兄弟会导致ora 04031错误:
那么如何评估gcs的大小?
从上图红线可以看出他的大小依赖于db buffer的大小。
当实例高速缓存buffer cache增加的时候,gcs资源所占用的空间也相应增长，具体算法如下：Example with Linux x86-64 / 10.2.0.4
o v$resource_limit
Resource Name Current Max Initial Limit
-------------- ------- ------- ------- -------
gcs_resources 585758 1110251 1113203 1113203
gcs_shadows 909888 1111054 1113203 1113203
o Initial shared memory in theory,
gcs resources = 1113203 * 120(+alpha) bytes = 133,584,360 (+alpha) bytes
gcs shadows = 1113203 * 72(+alpha) bytes = 80,150,616 (+alpha) bytes
o Actual size in shared pool
gcs resources = 185,766,864 bytes
gcs shadows = 107,993,760 bytes
Practically, a little bigger memory is used because gcs resources/shadows
structure sizes are different depending on Oracle versions and platforms.
也就是加大shared_pool 。
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