【Oracle】删除大表操作一則

      因為資料庫空間不足，需要對曆史資料進行清理，查詢涉及的表竟然有550G，和開發溝通之後将曆史資料使用應用程式遷移到其他機器上，之後對舊表進行删除！(對于此種情況多少有些無奈，入職之前表已經存在了，建表的時候應該考慮使用分區表，清理資料會更友善)

 檢視表的大小

YANG@yangdb>set timing on;

YANG@yangdb>SELECT segment_name,bytes/1024/1024/1024 FROM user_Segments WHERE segment_name='YANGTAB';

SEGMENT_NAME                   BYTES/1024/1024/1024

------------------------------ --------------------

YANGTAB                            550.075195

Elapsed: 00:00:00.98

YANG@yangdb>

使用 truncate的reuse storage 特性，預設時是drop storage，這樣會直接對object占用的删除之後并不直接drop storage ，這樣可以避免回收大量的extent 太多導緻系統資源緊張的情況

YANG@yangdb>truncate table YANG.YANGTAB reuse storage;

Table truncated.

Elapsed: 00:04:19.31

Elapsed: 00:00:00.09

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 563277M;

ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 563277M

*

ERROR at line 1:

ORA-03230: segment only contains 72099438 blocks of unused space above high water mark

Elapsed: 00:00:00.27

第一次 size 設定的有點大！

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 503277M;

Table altered.

Elapsed: 00:00:17.99

YANGTAB                            491.481628

Elapsed: 00:00:00.03

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 453277M;

Elapsed: 00:00:14.50

YANGTAB                            442.653503

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 403277M;

Elapsed: 00:00:14.86

YANGTAB                            393.825378

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 323277M;

Elapsed: 00:00:22.53

YANGTAB                            315.700378

Elapsed: 00:00:00.02

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 253277M;

Elapsed: 00:00:28.05

YANGTAB                            247.341003

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 183277M;

Elapsed: 00:00:54.36

YANGTAB                            178.981628

Elapsed: 00:00:00.13

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 123277M;

Elapsed: 00:00:33.64

YANGTAB                            120.387878

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 83277M;

Elapsed: 00:00:22.36

YANGTAB                            81.3253784

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 53277M;

Elapsed: 00:00:14.35

YANGTAB                            52.0285034

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 33277M;

Elapsed: 00:00:09.40

YANGTAB                            32.4972534

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 13277M;

Elapsed: 00:00:09.29

YANGTAB                            12.9660034

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 3277M;

Elapsed: 00:00:04.44

YANGTAB                            3.20037842

YANG@yangdb>ALTER table YANG.YANGTAB DEALLOCATE UNUSED KEEP 277M;

Elapsed: 00:00:03.08

YANGTAB                            .270690918

Elapsed: 00:00:00.07

YANG@yangdb>drop table YANG.YANGTAB;

Table dropped.

Elapsed: 00:00:01.11

YANG@yangdb>SELECT segment_name,bytes/1024/1024/1024 FROM user_Segments WHERE segment_name='YANGTAB_NEW';

YANGTAB_NEW                        83.7783203

Elapsed: 00:00:00.01

YANG@yangdb>rename YANGTAB_new to YANGTAB;

Table renamed.

Elapsed: 00:00:00.10

YANGTAB                            83.7783203

<b>附上操作過程中遇到的低級錯誤</b>

<b>1 oracle 和mysql 之間對表的重命名的文法混淆了，汗！</b>

YANG@yangdb&gt;rename table YANG.YANGTAB_new to YANG.YANGTAB;

rename table YANG.YANGTAB_new to YANG.YANGTAB

       *

ORA-00903: invalid table name

<b>2 表名不允許帶owner</b>

YANG@yangdb&gt;rename YANG.YANGTAB_new to YANG.YANGTAB;

rename YANG.YANGTAB_new to YANG.YANGTAB

ORA-01765: specifying owner s name of the table is not allowed

參考自己的另一篇文章

<a href="http://space.itpub.net/22664653/viewspace-704778">http://space.itpub.net/22664653/viewspace-704778</a>