Oracle

Analyze table tablename compute statistics; Analyze index indexname compute statistics;   It is very beneficial to use CBO, and more reliable table information can be used, so that the execution plan can be more accurate. In 10 Gb, analyze

  The backup and recovery capabilities are "broken. The principle is briefly introduced here:   Oracle records the changes of all data files in the form of logs. Therefore, as long as all ORACLE data files are backed up in a certain period of

InProduction environment, we will find: ① The index tablespace I/O is very high② The "DB file sequential read" Wait event is also relatively highThis shows that the entire database system and indexes have many read/write operations and have become

InOne frequency Commit/rollbackOr disk I/O problems, a large number of physical read/write contention So we will often see Log File sync wait events appear in top events The metrics for evaluating Log File sync wait events are the average wait time

I still want to worry about it. If you want to learn the Oracle architecture thoroughly, you must learn it based on the backup and recovery experiments and principles. I will also write a blog later. Here I am introducing the memory structure, just

1) There are two rows in the statistics that are related to performance. 15 SQL*Net roundtrips to/from client 198 rows processed The first line indicates the number of rounds from buffer cache to PGA. The second row indicates the number of rows

Given the longitude and latitude of 2 points, the distance between the points is calculated by using Java code and the Oracle stored procedure (in meters) Oracle stored procedure: Create or replace procedure sp_get_distance (CX in number, cy in

Diagnostic file (diagnostic file)1: Role of diagnostic files Diagnostic files:Contains information about major events in the background.Used to resolve problems,Used for daily log file management.2: Classification of diagnostic file logs There are

This ORA-38301 occurs when a stored procedure creates a table: the DDL/DML error cannot be performed on objects in the recycle bin. It turns out that this is a new 10 Gb feature, recycle bin. Drop tables are not directly deleted. It is placed in the

1. View All Users:Select * From dba_users;Select * From all_users;Select * From user_users; 2. view system permissions of users or roles (system permissions assigned to users or roles ):Select * From dba_sys_privs;Select * From user_sys_privs;   3.

When lgwr is idle, it depends on the rdbms rpc message wait event and is in sleep state until three seconds. If lgwr finds that redo information needs to be written, then lgwr will execute the write operation, and the log file parallel write wait

What is a flashback recovery zone? Oracle 10g has a new feature called automatic disk-based backup and recovery ). The basis for implementing this function is the flash recovery area described in this article ). Flash recovery zone is a new feature

I. Technical Points 1. dbms_obfuscation_toolkit.md5Dbms_obfuscation_toolkit.md5 is an MD5-encoded data packet function, but an error message is displayed when select dbms_obfuscation_toolkit.md5 (input_string => 'abc') A from dual, it seems that

The following describes the Import and Export instances.Data export:1. Export the database test completely, and the username System Password Manager is exported to D: \ daochu. dmp.Exp system/manager @ test file = D: \ daochu. dmp full = y2. Export

1. First, let's take a look at the differences between Oracle and sqlserver. A database in Oracle is an instance, while in SQL Server, multiple databases can be created under an instance. From the user perspective, one Oracle user is a schema

Oracle Data Import and Export dmp 1: Start-> Run-> cmd-> exp-> User Name/password @ connection word (DBA permission is required for full Database Export)-> press ENTER-> enter the export path (C: /AA. DMP)-> select (E, U or T) as required-> press

View users with sysdba Permissions Log on to Oracle as a sys user and execute select * from V _ $ pwfile_users; the following results can be queried: SQL> select * from V _ $ pwfile_users; Username sysdba sysoper -------------------------------------

Top-level users: Username: SYS Link: sysdba Role creation: /* Create the Customs V2.0 configuration library */drop tablespace cms_para including contents and datafiles; Create tablespace cms_para logging datafile 'd: \ oracle \ oradata \ orcl \

　 1. There are two ways to run Oracle databases: (1) archivelog: Archive aims to restore the database to the maximum extent when a database fails. It ensures that no submitted data is lost: (2) Non-archive mode (noarchivelog): Only the database can

The following example shows how to import and export ORACLE data to a user in another database: Exp userid = system/manager owner = username1 file = expfile. dmp IMP userid = system/manager fromuser = username1 touser = username2 ignore = y file =