标签云
asm恢复 bbed bootstrap$ dul In Memory kcbzib_kcrsds_1 kccpb_sanity_check_2 MySQL恢复 ORA-00312 ORA-00607 ORA-00704 ORA-00742 ORA-01110 ORA-01555 ORA-01578 ORA-08103 ORA-600 2131 ORA-600 2662 ORA-600 2663 ORA-600 3020 ORA-600 4000 ORA-600 4137 ORA-600 4193 ORA-600 4194 ORA-600 16703 ORA-600 kcbzib_kcrsds_1 ORA-600 KCLCHKBLK_4 ORA-15042 ORA-15196 ORACLE 12C oracle dul ORACLE PATCH Oracle Recovery Tools oracle加密恢复 oracle勒索 oracle勒索恢复 oracle异常恢复 Oracle 恢复 ORACLE恢复 ORACLE数据库恢复 oracle 比特币 OSD-04016 YOUR FILES ARE ENCRYPTED 勒索恢复 比特币加密文章分类
- Others (2)
- 中间件 (2)
- WebLogic (2)
- 操作系统 (103)
- 数据库 (1,714)
- DB2 (22)
- MySQL (74)
- Oracle (1,574)
- Data Guard (52)
- EXADATA (8)
- GoldenGate (24)
- ORA-xxxxx (160)
- ORACLE 12C (72)
- ORACLE 18C (6)
- ORACLE 19C (15)
- ORACLE 21C (3)
- Oracle 23ai (8)
- Oracle ASM (68)
- Oracle Bug (8)
- Oracle RAC (53)
- Oracle 安全 (6)
- Oracle 开发 (28)
- Oracle 监听 (28)
- Oracle备份恢复 (574)
- Oracle安装升级 (94)
- Oracle性能优化 (62)
- 专题索引 (5)
- 勒索恢复 (81)
- PostgreSQL (18)
- PostgreSQL恢复 (6)
- SQL Server (28)
- SQL Server恢复 (9)
- TimesTen (7)
- 达梦数据库 (2)
- 生活娱乐 (2)
- 至理名言 (11)
- 虚拟化 (2)
- VMware (2)
- 软件开发 (37)
- Asp.Net (9)
- JavaScript (12)
- PHP (2)
- 小工具 (20)
-
最近发表
- 使用sid方式直接访问pdb(USE_SID_AS_SERVICE_LISTENER)
- ORA-00069: cannot acquire lock — table locks disabled for xxxx
- ORA-600 [4000] [a]相关bug
- sql server数据库“正在恢复”故障处理
- 如何判断数据文件是否处于begin backup状态
- CDM备份缺少归档打开数据库报ORA-600 kcbzib_kcrsds_1故障处理
- ORA-07445: exception encountered: core dump [expgod()+43] [IN_PAGE_ERROR]
- 2025年第一起ORA-600 16703故障恢复
- _gc_undo_affinity=FALSE触发ORA-01558
- public授权语句
- 中文环境显示AR8MSWIN1256(阿拉伯语字符集)
- 处理 Oracle 块损坏
- Oracle各种类型坏块说明和处理
- fio测试io,导致磁盘文件系统损坏故障恢复
- ORA-742 写丢失常见bug记录
- Oracle 19c 202501补丁(RUs+OJVM)-19.26
- 避免 19c 数据库性能问题需要考虑的事项 (Doc ID 3050476.1)
- Bug 21915719 Database hang or may fail to OPEN in 12c IBM AIX or HPUX Itanium – ORA-742, DEADLOCK or ORA-600 [kcrfrgv_nextlwn_scn] ORA-600 [krr_process_read_error_2]
- ORA-600 ktuPopDictI_1恢复
- impdp导入数据丢失sys授权问题分析
标签归档:library cache latch
library cache latch等待事件
产生library cache latch原因
The library cache latches protect the cached SQL statements and objects' definitions held in the library cache within the shared pool. The library cache latch must be acquired in order to add a new statement to the library cache. During a parse, Oracle searches the library cache for a matching statement. If one is not found, then Oracle will parse the SQL statement, obtain the library cache latch and insert the new SQL.
每一个sql被执行之前,先要到library cache中根据hash_value查找parent cursor,这就需要先获得library cache latch;找到parent cursor后,就会去查找对应的child cursor,当发现无法找到时,就会释放library cache latch,获得share pool latch分配空间给硬解析后的产生的执行计划;然后再次获得library cache latch进行把执行计划放入share pool,转入library cache pin+lock(null模式)开始执行sql.library cache latch 的个数有限(与CPU_COUNT参数相关),当数据库中出现大量硬解析的时候,某一个sql无法得到library cache latch就会开始spin,达到spin count后还没得到,就会开始sleep,达到sleep时间后,醒来还再次试图过的library cache latch得不到就在spin再得不到又sleep…依此类推.
综上可知:在sql执行的过程中可以看出在出现High Versions Count和Hard Parse的情况下都有可能出现library cache latch等待.
关于Hard Parse见:shared pool latch 等待事件
关于High Versions Count见:关于High Versions Count总结
1._KGL_LATCH_COUNT控制library cache latches数量
The hidden parameter _KGL_LATCH_COUNT controls the number of library cache latches. The default value should be adequate, but if contention for the library cache latch cannot be resolved, it one may consider increasing this value. The default value for _KGL_LATCH_COUNT is the next prime number after CPU_COUNT. This value cannot exceed 67.
2.Library cache: mutex X
在10g及其以后版本中,很多latch使用mutex代替,我们常见的Library cache: mutex X is similar to library cache wait in earlier version.(_kks_use_mutex_pin=false可以禁止mutex)