Fragmentation / Defragmentation Of Space In Database
Jul 31, 2012
Oracle DB version : 10.2.0.5.0
OS version HP-UX B.11.31 U ia64
DB size : 2TB
We have the above configuration for one of our oracle database. One of our DBA acts like he is only the person on this earth who is managing the process of fragmentation removal from the tablespaces in order to improve the performance and wastage of the space. He performs that task at weekends and takes one-off day extra. I am not sure how the fragmentation removal improves the performance and deallocates the space.
Is it compulsory to perform the rebuild process weekly in order to remove fragmented space from tablespaces? Do we have any other method to automatically re-organize objects occupying waste space?
Why the reuild of indexes using separate tablespace improves performance? is there any specifi reason for it?
I got the error ORA-01653: unable to extend table <OWNER.TABLE_NAME> by <BYTE> in tablespace <TABLESPACE> in my production database. But I could see 4GB of free space available in the tablespace. But this was resolved after increasing the Tablespace size by 1 more GB. So I wanted to know how I can I reclaim the 4GB space ?
While searching in internet I got few tips like there will be a fragmentation in the tablespace, the free space available in the tablespace may not be a continuous block. To avoid this we need to reorganize the tables using ALTER TABLE <TABLE_NAME> MOVE <TABLESPACE>; command.
But in my tablespace there are huge number of tables exists I cannot do reorganization of all the tables. So I need to know how to identify particularly what are the tables has more fragmentation? so that I can go for reorganizing those tables only.
My Database version in 9.2.0.7 Tablespaces are Locally Managed
I need to monitor the Database daily, so i need to check whether the size of the DB is increasing @ a slow rate or rather than that. I need to do it in RAC & NON-RAC.
I am having an issue with the LOBs in our Database. Our production DB is about 71G right now - if i do export/import using the DataPump - I see the data volume becomes 40G. I am sure its because of the LOBs in my Database. Our application uses lots of LOB datatype and I think the space is not being released.
The challenge is I cant do a full export/import in my Production DB as its a 24/7 system and to do export/import I need min. 5 hrs - which my business will not permit. I can I claim the unused space here. I have used Segment Advisor - but it has only given me 6G of space gain.
Is there any script I can try to use to reclaim space in the database.
First one : ----------------- 1)Created a backup table from the Fragmented table (This table is a partitioned one). 2)Analyzed this table. 3)DROP the Fragmented table 4)Inserted the backuped up data from backup table to the Re-created table. 5)Analyze this table.
Second method ------------------- 1) Create a backup table newly, with PCTFREE =0 2) Inserted the data from Fragmented table ( This is a partitioned table) to backup table 3) Analyzed this table. 4) Truncate Fragmented table 4) Did Exchange partition of Fragmented table with Backup table.
The second method is not found to be removing the Fragmentation. Before the fragmentation was 28% after Second method the fragmentation is still the same. While the first method the fragmentation reduced to 16%.
Query used to find Fragmentation. select table_name, round((blocks*8),2) "table size kb", round((num_rows*avg_row_len/1024),2) "actual data in table kb", round((blocks*8),2)- round((num_rows*avg_row_len/1024),2) "wasted space kb",
Does "Update on a Partitioned Column" cause fragmentation ?
See example below :
Suppose I have a table as below that has approx 3 million rows and growing :
1) Table ABC : file_id number status_flag varchar2(1) file_Content clob date_created date
2) This table is list partitioned on Column "status_flag".
Column "status_flag" can take 3 values "A" or "B" or "C"
3) A file_id can transition from 1 "Status_flag" to another. [ A--> B , C--> B, B-->C, A --> C, etc ]
This means its possible to UPDATE the "status_flag " - the partitioned column.
Question : ------------- 1) Would the movement of rows from 1 partition to another cause fragmentation ? 2) Or Instead, should this be achieved by maintaining 3 tables - 1 each for every "status_Flag" as Table_A, Table_B, Table_C
This would mean that, if file_id 1, changes "status_flag" from 'A' to 'B' : -- The corresponding row from Table_A will be created in Table_B --- The same will be deleted from Table_A
This would still cause fragmentation ... with the overhead of Inserting a CLOB column from 1 table to another.
3) How to determine how much percent of the table is fragmented ?
Sysaux Tablespace is running low. WE SET AWR RETENTION TIME=60 DAYS. WE ARE NOT INTEREST TO EXTEND SYSAUX TABLESPACE SIZE. Usually we take AWR weekly once. Some times we did ADDM report and ASH.
CODEsql>select TABLESPACE_NAME, FILE_NAME, BYTES/(1024*1024), AUTOEXTENSIBLE, MAXBYTES/(1024*1024) from dba_data_files where tablespace_name = 'SYSAUX';
1. What's the best SOLUTION ? 2. Can i shrink sysaux tablespace ? 3. I think , The size for all occupants in sysaux tablespace is less than 200 MB => how to find actual content of sysaux tablespace ? 4. What could be the reason for growth? Is there any way to free the space from sysaux table space?
I want to do horizontal fragmentation of a table say employee. But fragmentation is often related to distributed databases. So i want to ask how can i do this on my single home computer? list out the steps that should be performed. I saw the concept of link but really failed to understand that.
I have tried below steps for removing the table fregmentation but for some table i am not getting good result here.
1. It will collect the data which are having more than 100MB fragmentation.
select owner,table_name,blocks,num_rows,avg_row_len,round(((blocks*8/1024)),2)||'MB' "TOTAL_SIZE", round((num_rows*avg_row_len /1024/1024),2)||'Mb' "ACTUAL_SIZE", round(((blocks*8/1024)-(num_rows*avg_row_len/1024/1024)),2) ||'MB' "FRAGMENTED_SPACE" from dba_tables where owner in('a','b','c','d') and round(((blocks*8/1024)-(num_rows*avg_row_len/1024/1024)),2) > 100 order by 8 desc;
2. then move the object(table) to the same tablespace.
alter table abc move; alter table bcd move; alter table efg move;
3. also rebuild the dependent objects.
alter index abc_PK rebuild online;
4. Then analyze the table which are having more than 100MB of fragmentation.
I am trying to find the space occupied on disk by the tablespaces of the database that contain tables, some (and not all) of whose columns are encrypted. My query is like this:
select distinct a.tablespace_name, file_name, bytes /(1024*1024*1024) File_Size_In_GB from dba_data_files a, dba_tables b, (select distinct owner, table_name from DBA_ENCRYPTED_COLUMNS) c where a.tablespace_name = b.tablespace_name and b.owner = c.owner and b.table_name = c.table_name order by a.tablespace_name;
The output of the query is as shown in the attached file:
Since the output (under the heading Total Size of the tablespace) is probably the sum of all the datafiles returned by the query and is obviously incorrect, I have not given the rest of it. I also tried the following:
select distinct a.tablespace_name, file_name, bytes /(1024*1024*1024) File_Size_In_GB, sum (bytes/(1024*1024*1024))over (partition by a.tablespace_name order by file_name) "Total Size of the tablespace" from dba_data_files a, dba_tables b, (select distinct owner, table_name from DBA_ENCRYPTED_COLUMNS) c where a.tablespace_name = b.tablespace_name and b.owner = c.owner and b.table_name = c.table_name order by a.tablespace_name ; [code]...
Here, the fig. under the heading "Total Size of the tablespace" are probably the sum of all the records returned by the query if distinct is not used i.e all the data file sizes returned by the query.
tune my query and get the desired results? I think this can be achieved by group by with rollup, cube, order by and grouping functions, but am not sure how to proceed. I know that I can get the results by using Enterprise Mgr. Console in 2 mins., but would still like to get the results with the queries.
In OEM10 I can click on the database size in the database page. When I do this I am redirected by the OEM to teh Database space usage report.
I have 3 questions about reports in OEM10g:
1. Can I create drill-down reports in OEM10g?I want to create a report that shows the space usage per host and drill down to the databases (targets) that are on that host.
2.Can I create a link to the Database space usage report? I would like to redirect to the report from the report in question 1 from a target. So that I can see the space usage of the database that was selected.
3. Can I create a copy of the Database Space Usage summary report that the OEM shows? I can't find it in the report tab of the OEM.
I want to change space allocation for character columns in my database, So it will store them as 'CHAR' and not 'BYTE'.my character set is
SQL> SELECT VALUE FROM V$NLS_PARAMETERS WHERE PARAMETER='NLS_CHARACTERSET'; VALUE ---------------------------------------------------------------- AL32UTF8 SQL> alter system set NLS_LENGTH_SEMANTICS='CHAR' scope=both;
System altered.I bounced the instance just to make sure
And then I want to see that when I create a table with some varchar2 column,The space for it will be allocated by chars, and not by bytes! However, when I run a check of create table, this is what I get:
I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
i have data about 3 gb but my files in e:oraclexeapporacleoradataXE has grown to 16 gb
1)my e: drive has less space ,pls tel how can i fee some space and give it back to OS
2)is there any other place where i can free up some space from oracle and give it back to OS.
----------------------- windows (2008) --- Oracle Database 11g Express Edition Release 11.2.0.2.0 - Production PL/SQL Release 11.2.0.2.0 - Production "CORE 11.2.0.2.0 Production" TNS for 32-bit Windows: Version 11.2.0.2.0 - Production (2008) NLSRTL Version 11.2.0.2.0 - Production
