Oracle

1. Display current user index information (dba_indexes,all_indexes,user_indexes) 03:41:37 sql> Select Index_name,index_type,uniqueness 03:41:49 2 from User_indexes; Index_name Index_type Uniquenes --------------- --------------- ---------

1, prohibit the restriction 04:55:47 sql> ALTER TABLE t1 disable novalidate constraint; Table altered. 04:55:48 sql> Select Constraint_name,constraint_type,status,table_name from user_constraints 04:56:03 2 where table_name= ' T1 ';

1. View System permissions sql> desc System_privilege_map; Name Null? Type ----------------------------------------------------------------- -------- -------------------------------------- ------ Privilege not NULL number NAME not NULL VARCHAR2

When does an instance recovery occur? When your database server is powered down abnormally, an instance recovery occurs when you restart the database. Instance recovery is done automatically by the database without the intervention of the DBA. Of

One, what is redo LOG The Redolog file is a very important document that records all changes to Oracle and is the most critical component of the database instance recovery mechanism. Sys@ocm> select * from V$log; group# thread# sequence# BYTES

1. The function and influence of the lock Locks are one of the core mechanisms for Oracle to manage concurrent access to shared database resources and to prevent "mutual interference" between concurrent database transactions. When the application

Selection rate (selectivity): selection rate is the ratio of the rows that meet the criteria to the result set of the query 1. Assuming there are 120 people in the classroom, how can we determine how many of them have birthdays in October?12 months

1, the column to row, the following data ID NAME ---------- ------------------------------ Ten AB bc Ten CDs Hi ij Mn 6 Rows selected 2. Call Oracle's function Sql> Select Id,wmsys.wm_concat (name) name from IDTable 2 Group by ID; ID NAME ---------

Width-bucket returns the bucket number to which the current record belongs, based on the parameter settings. The syntax format is as follows: Width_bucket (expression, minval expression, maxval expression, num buckets) The first argument is a

1. In addition to using numbers to specify the window range, we can also use date types such as: 2.lead and Lag, returns a record in the current window that is n from the current record. Lag for forward record, lead for backward fetch record

This article introduced a four user synchronization update stored procedure instance, through this example study, you may discover that the temporary table under certain condition also can be nimble and easy to use, when the data quantity is small,

Parent-child Cursor (parent-child cursor) Parent cursors: They correspond to the same parent cursor as long as the SQL statements have the same text. Sub-cursors: In some cases, although the text of the SQL statement is the same, it causes

The following four SCN are primarily present within Oracle 1. Systems checkpoint (System checkpoint) SCN Each time a checkpoint completes, Oracle records the SCN corresponding to the checkpoint in the control file and can view the checkpoint SCN

1.Back Up Database Rman Backup Under normal circumstances 2. Backup OCR and vote disk [Root@rac2 bin]#./ocrconfig-export/tmp/ocr_export.bak [Root@rac2 bin]# More/etc/oracle/ocr.loc Ocrconfig_loc=/dev/raw/raw11 Local_only=false [Root@rac2 bin]#

-------Line Links /*** rebuilding data rows across multiple blocks of data In a production environment, data changes cause many rows of data to be stored in multiple data blocks. This results in an increased frequency of IO usage and further

There was a problem with the system last night, a stored procedure was performing an exception, and observation only found that the higher the logic read. When the situation was more urgent, I had to change the original into the old way. In fact,

Principles of Database Physics design 1.1 Database Environment Configuration principles 1.1.1 Operating System Environment: For small and medium-sized database system, the use of Linux operating system is more appropriate, for the database

In an Oracle database, creating an index is relatively straightforward. However, it is more difficult to create indexes reasonably. The author believes that when creating an index, it is three appropriate to create an appropriate number of indexes

In Oracle databases, a set of default user operating environments is provided. The number of rows fetched from the database once, such as when a user queries, the separator between columns, the maximum width per line, the number of rows by default

A lot of the time, do Oracle DBA us, when the application administrator to inform us that the application is now slow, the database is very slow, when we go to the database to do a few examples of select also found the same problem, sometimes we can