ITPub博客

1.2.4 Which Optimizer to Use? If you are currently using the rule-based optimizer, I strongly recommend that you transfer to the cost-based optimizer. Here is a list of the reasons why: • The time spent coding is reduced. • Coders do not need to be aware of the rules. • There are more features, and far more tuning tools, available for the cost-based optimizer. • The chances of third-party packages performing well has been improved considerably. Many third-party packages a

cle 8 数据链路在程式中不能支持：    ODBC        数据不可提交，无错误，偶尔会有错误。    Microsoft OLE DB         数据不可提交，无错误    Oralce OLE DB (在BPCS上可以，但在Cimprod不可以)       错误为:        ORA-02041: client database did not begin a transaction    Oracle的说明：cause: An update occurred a

/*理解Rule-based 优化器       RBO 优先使用预定义方法去计算使用的某条路径访问数据库资料.     RDBMS 使用下列条件则优先选择RBO的优化器.包括:在init.ora 文件中设定OPTIMIZER_MODE = RULE 在init.ora 文件中设定OPTIMIZER_MODE = choose,并且在SQL 中所包含的Table 没有统计资料. 在Session 中使用 alter session set optimizer_mode=rule 在Session 中使用 Alter session set optomizer_mode=Choose 命令,并且SQL 中的任何table 都没有统计资料  Rule hint (例如 select /*+RULE

Oracle8i,9i 中对Long 操作有一个限制.就是:所有的select,Update,lock tables 的所有Long columns 必须在同一个Database中. 而你的SQL,正好选取了两个long columns 分别在两个database 上.所以会出现 ora-00997 的错误. -----原始邮件-----发件人: Harrison Jiang 发送时间: 2005年4月19日 13:11收件人: Lis Li主题: all_tab_columnsselect a.column_name,a.data_type,a.data_length,a.nullable,a.data_default,b.data_type,b.data_length,b.nullable,b.data_defaultfrom all_tab_columns a,all_tab_columns@acmtest bwhere a.o

With the introduction of the 20 new database triggers, came the creation of attribute events or variables that are set when a certain database trigger event is executed. The previous section highlighted each of the database triggers, along with the event attributes that are set and can be referenced for each trigger. Below is a list of each of the attribute events, the data type and a short description.Attribute EventData TypeDescriptionora_client_ip_addressVARCHAR2Provides the IP address of the

There are six database system event triggers. The six database system event triggers are outlined below, along with a description and the event attributes that are set for each event.Database TriggerBEFORE/AFTER ExecutionDescriptionAttribute EventLOGOFFBEFOREExecuted when a user logs off, at the start of the logoff processora_syseventora_login_userora_instance_numora_database_nameLOGONAFTERExecuted when a user logs into the database, after a successful login of the userora_syseventora_login_user

DDL/Client EventsThere are 14 DDL/client event triggers and these can be created at the database level and will execute for all schemas, or these can be created at the schema level and will execute only for the schema it is created for. When a trigger is created at the schema level, the trigger is created in the schema specified and executes only for that schema.This provides a great deal of flexibility depending on your environment and what you want to monitor or respond to. The 14 DDL/client e

IntroductionCreation of Database TriggersA database trigger is created and dropped with the following commands:    CREATE OR REPLACE TRIGGER trigger_name (BEFORE|AFTER)                  database_trigger_event ON (DATABASE|schema.SCHEMA)…;    DROP TRIGGER trigger_name;When a database trigger is created, the trigger is checked for syntax, the dependency tree and privileges are checked,&nb