- Oracle 10g tablespace fragmentation how to#
- Oracle 10g tablespace fragmentation full#
- Oracle 10g tablespace fragmentation free#
So, that we can move this table to same or new tablespace.
Oracle 10g tablespace fragmentation free#
Find Current size of you table from dba_segments and check if same or any other tablespace has same free space available. In this step we will move fragmented table to same tablespace or from one tablespace to another tablespace to reclaim fragmented space. Select index_name,status from dba_indexes where table_name like '&table_name' We will record Index status at one place, So that we get back them after completion of this exercise, Option: 1 Alter table move (to another tablespace, or same tablespace) and rebuild indexes:-Ĭollect status of all the indexes on the table:.
![oracle 10g tablespace fragmentation oracle 10g tablespace fragmentation](https://image.slidesharecdn.com/fragmentation-110617144314-phpapp01/95/fragmentation-3-728.jpg)
Here, I am following Options 1 and 3 option by keeping table availability in mind. (Shrink command is only applicable for tables which are tablespace with auto segment space management) Export and import the table:- (difficult to implement in production environment) (Depends upon the free space available in the tablespace)Ģ. Alter table move (to another tablespace, or same tablespace) and rebuild indexes:. We have four options to reorganize fragmented tables:ġ. Suppose, DBA find 50% reclaimable space by above query, So he can proceed for removing fragmentation.Ĥ. If you find reclaimable space % value more than 20% then we can expect fragmentation in the table. Note: This query fetch data from dba_tables, so the accuracy of result depends on dba_table stats. Database Administrator has to provide table_name and schema_name as input to this query. Select table_name,bytes/(1024*1024*1024) from dba_table where table_name='&table_name' īelow query will show the total size of table with fragmentation, expected without fragmentation and how much % of size we can reclaim after removing table fragmentation. Now again check table size using and will find reduced size of the table. Other wise i would suggest to gather table stats to get updated stats.Įxec dbms_stats.gather_table_stats('&schema_name','&table_name') If this value is recent you can skip this step. Check LAST_ANALYZED value for table in dba_tables. So, We have to have updated stats on the table stored in dba_tables. The difference between these value will report actual fragmentation to DBA. To check exact difference in table actual size (dba_segments) and stats size (dba_tables). Steps to Check and Remove Table Fragmentation:. This all is due to fragmentation in the table or stats for table are not updated into dba_tables.
![oracle 10g tablespace fragmentation oracle 10g tablespace fragmentation](https://slideplayer.com/slide/1514365/5/images/41/Tablespace+Planning+Use+locally+managed+tablespaces+(LMTs)+with+UNIFORM+size+extents.+64K+bitmaps+on+file+header+are+used+to+manage+extents..jpg)
In Oracle schema there are tables which has huge difference in actual size (size from User_segments) and expected size from user_tables (Num_rows*avg_row_length (in bytes)).
Oracle 10g tablespace fragmentation full#
Note: Index based queries may not get that much benefited by reorg as compared to queries which does Full table scan. What are the reasons to reorganization of table?Ī) Slower response time (from that table)ī) High number of chained (actually migrated) rows.Ĭ) Table has grown many folds and the old space is not getting reused.
![oracle 10g tablespace fragmentation oracle 10g tablespace fragmentation](https://docs.oracle.com/cd/B25329_01/doc/admin.102/b25107/img/xedba006.gif)
Since Oracle knows that blocks beyond the high water mark don't have data, it only reads blocks up to the high water mark when doing a full table scan. Blocks below the high water mark (used blocks) have at least once contained data. HWM is an indicator of USED BLOCKS in the database.
![oracle 10g tablespace fragmentation oracle 10g tablespace fragmentation](https://docplayer.net/docs-images/40/12846839/images/page_7.jpg)
When a lot of DML operations are applied on a table, the table will become fragmented because DML does not release free space from the table below the HWM. Note that table fragmentation is different from file fragmentation. When rows are not stored contiguously, or if rows are split onto more than one block, performance decreases because these rows require additional block accesses. To understand it more clearly, we need to be clear on how oracle manages space for tables. This leaves behind holes in table which results in table fragmentation. The space which gets freed up during non-insert DML operations is not immediately re-used (or sometimes, may not get reuse ever at all). If a table is only subject to inserts, there will not be any fragmentation.įragmentation comes with when we update/delete data in table.
Oracle 10g tablespace fragmentation how to#
How to find Table Fragmentation in Oracle Database