I prefer the version 11.2.0.3 parse_calls (我比较喜欢parse_calls在11203版本上的显示)
高parse calls表示这些SQL不可以re-used 并且每次执行都要重新解析，理想的最佳状态是一次解析多次执行，你也知道频繁的解析会给library cache带来沉重的负担， 一个sql的执行必须先parse，解析过程包含sql 加载到shared pool, 语法检查…
Logon Storms on 11g ,audit maybe cause performance issue.(当创建很多连接时审计可能带来性能问题)
When multiple connection created will insert a lot of rows in aud$ table, there may be contention in the segment header for the table. This contention can manifest itself as a buffer busy wait or a freelist wait.
Unable to change MEMORY_MAX_TARGET (无法修改MEMORY_MAX_TARGET)
alter system set memory_max_target=0 scope=spfile;
shutdown immediate
startup
SQL> show parameter target
…
memory_max_target big integer 3824M
Logon Storm and Memory shortage issue ORA-07445 dbgtrReserveSpace (记录一次登录风暴致内存不足的问题)
Exception [type: SIGSEGV, Address not mapped to object] [ADDR:0x10] [PC:0x938E8C5, dbgtrReserveSpace()+99] [flags: 0x0, count: 1]
Errors in file /oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_13864.trc (incident=60801):
ORA-07445: exception encountered: core dump [dbgtrReserveSpace()+99] [SIGSEGV] [ADDR:0x10] [PC:0x938E8C5] [Address not mapped to object] []
Incident details in: /oracle/diag/rdbms/ora11g/ora11g/incident/incdir_60801/ora11g_ora_13864_i60801.trc
Use ADRCI or Support Workbench to package the incident.
scn format (scn格式)
scn(system change number) 结构主要维护 oracle数据库内部的数据一致性，SCN 有两部分组成: Base and wrap，wrap 是16bit的数字，base是32bit的数字,这样其实就可以算scn的有效范围，它的格式(redo dump trace)是wrap.base，当base超过了2的32次方,然后wrap 就会加1，其实用sql 很好验证。
SQL Test Case Builder generate test case automatically(自动生成SQL所需测试数据)
Why SQL Test Case Builder? For most SQL problems, the s […]
ORA-00313,ORA-00312,ORA-27037,ORA-19527 DATAGARD 11G r2
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
DDE: Problem Key ‘ORA 312’ was flood controlled (0x5) (no incident)
ORA-00312: online log 2 thread 1: ‘/oracle/oradata/icme/redo02.log’
Error 19527 creating/clearing online redo logfile 2
Send email using utl_smtp in Oracle 11g (results in ORA-24247)(11g ACL 网络访问控制列表)
ORA-24247: network access denied by access control list (ACL)
ORA-06512: at “SYS.UTL_TCP”, line 17
ORA-06512: at “SYS.UTL_TCP”, line 267
Oradebug Security
DEMO 1,How to use oradebug to call OS commands via the database
DEMO 2,Disable sys audit
How to imp job to another schema in same db(同一数据库导入JOB到另外一用户)
ORA-39083: Object type JOB failed to create with error:
ORA-00001: unique constraint (SYS.I_JOB_JOB) violated
Dynamically Changing shared_pool_size fail!(动态修改Shared pool size失败)
因安装数据库时启用了ASMM,过了几天发现分配不太理想想禁用ASMM，手动调整shared_pool_size, 这是一个动态参数，修改后立即生效无需重启数据库实例，但修改时遇到了比较奇怪的现象。
ORA-07445 [kggchk()+77] [SIGSEGV] [Address not mapped to object]
今天有个项目系统负载突然变大，查到top sql是一个存储过程,执行计划缺少合理的索引，SQL是个update […]
export data from 11g and import into 10G R2 ORA-01455
EXP-00008: ORACLE error 1455 encountered
ORA-01455: converting column overflows integer datatype
EXP-00000: Export terminated unsuccessfully
Dynamic SQL Supports Statements Length Characters Limit (execute immediate sql长度限制)
有时需要在plsql 写一些动态sql,用execute immediate 或dbms_sql 调 用，但是execute immediate 后动态sql 文本的长度限制是多少呢？
To hold the latch manually, DB hang demo(手动持用latch使数据库hang)
It is widely known that the Oracle server uses kslgetl – Kernel Service Lock Management Get Latch function to acquire the latch,oradebug call kslgetl/kslfre can be used to acquire the latch manually. This is very useful to simulate latch related hangs and contention.
Delete the data on the table very slow(删除数据慢)
今天开发的同事问有个表上的数据为什么删不掉？我看了一下，也就不到100000条数据，表上有外键，等了5分钟hang在那里…
Know more about Oracle ASH
《Know More about Oracle AWR》 姐妹篇，oracle 10g引入，ASH 是性能诊断工具，不像sql trace总是默认打开， 保存历史上发生了什么， 提供比AWR更细粒度的数据，即使当系统负载很高时，它也工作的很好，因为使用类似memcopy的数据收集，不会有太大的额外负担，没用任何类型的数据库lock。 Active(‘Active’ == Non-idle sessions) Session History Licensed as part of the Diagnostic pack,
Know More about Oracle AWR
一段时间以来，Oracle在此领域的解决方案一直是其内置工具Statspack。Oracle数据库10g进行了重大改进：自动工作量存储库（AWR）。AWR与数据库一起安装，不仅捕获统计信息，还捕获捕获的指标。
Oracle 12c new feature:OFFSET n FETCH n row-limit
在分页查询或top n中在oracle 之间的版本使用rownum,row_number..，从12c 提供了offset fetch 的语法，其实这个语法不是什么新鲜玩意，在DB2,MSSQL,MYSQL,PostgreSQL之前也都提供的语法。
