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How to check whether table has been fragmented or not. I have googled it but dint get satisfactory response. what should be the ideal time or period to analyze the table.
Onkar TiwariOnkar Tiwari
1 Answer
what is your definition of fragmentation? Jonathan Lewis has given a good definition in https://jonathanlewis.wordpress.com/2010/07/13/fragmentation-1/. I think, it's hard to tell, when a table should be reorganized to reclaim space, that is no longer used. Ignoring LOBs, compression and other special cases, you can compare the actual size of a segment (in
dba_segments
) with the value you get by the multiplication of num_rows
with avg_row_len
in user_tables
(after a statistics gathering) - but I would hesitate to define a threshold signalizing the need for a rebuild; especially since this rebuild will change the physical order of rows and conequently the clustering factor
of related indexes: and this means - their efficiency.Martin PreissMartin Preiss
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IssueSQL Queries taking longer than normal to complete.
Product
Struxureware Power Monitoring
Power Monitoring Expert
ION Enterprise
ION EEM
Environment
SQL Server 2005, SQL Server 2008 R2, SQL Server 2012, SQL Server 2014, SQL Server 2016
Cause
When a database is frequently updated via INSERT, UPDATE, or DELETE statements we can expect it to become fragmented over the time.
If database indexes are fragmented, the SQL Server query optimizer may chose a non-optimal execution plan when using an index to resolve a query.
This will affect the overall query performance and you may notice a query behaving slower than normal.
Resolution
*Warning: Irreparable database damage can occur. This procedure should only be performed by users familiar with SQL Server Management Studio. Databases should be backed up prior to performing this procedure.*
The following is a simple query that will list every index on every table in your database, ordered by percentage of index fragmentation.
dbtables.[
name
]
as
'Table'
,
indexstats.avg_fragmentation_in_percent,
FROM
sys.dm_db_index_physical_stats (DB_ID(),
NULL
,
NULL
,
NULL
,
NULL
)
AS
indexstats
INNER
JOIN
sys.tables dbtables
on
dbtables.[object_id] = indexstats.[object_id]
INNER
JOIN
sys.schemas dbschemas
on
dbtables.[schema_id] = dbschemas.[schema_id]
INNER
JOIN
sys.indexes
AS
dbindexes
ON
dbindexes.[object_id] = indexstats.[object_id]
WHERE
indexstats.database_id = DB_ID()
ORDER
BY
indexstats.avg_fragmentation_in_percent
desc
This query can be modified to focus on specific tables by append the table name to the 'where' clause:
WHERE indexstats.database_id = DB_ID() AND dbtables.[name
] like '%%'
In order to reduce fragmentation we will have to reorganize or rebuild the indexes. Choosing between reorganizing or rebuilding depends on the query results.
For heavily fragmented indexes a rebuild process is needed, otherwise index reorganization should be sufficient.
The following table summarizes when to use each one:
Reference Values (in %) | Action | SQL statement |
avg_fragmentation_in_percent > 5 AND < 30 | Reorganize Index | ALTER INDEX REORGANIZE |
avg_fragmentation_in_percent > 30 | Rebuild Index | ALTER INDEX REBUILD |
Is there any way to check whether a table or index has been fragmented?
How to check if table is fragmented or not?
How to check if index is fragmented?
I searched Google but didn't get satisfactory answers. Some points like explain plan, table fragmentation, index rebuild etc I got. But what should be our first step and how should be resolve. How step by step we can move forward to resolve the issue?
Paul White♦57k1515 gold badges300300 silver badges474474 bronze badges
Onkar Tiwari
migrated from stackoverflow.comAug 31 '18 at 9:20
This question came from our site for professional and enthusiast programmers.
3 Answers
You need to use
INDEX_STATS
view to determine fragmentation. Firstly, You need to populate this view with an individual index by using :
and then look at these values
ratio
and height
:If ratio is more than %20
or height is more than or equal to 4
or lf_rows is lower than lf_blks,
Sql Query To Check Table Fragmentation In Oracle
then you need to rebuild your index against fragmentation.
The
blevel
column of dba_indexes
table is my main point of interest. This gives the number of branch levels (including the root node) for a b-tree index, and the column height
is closely related to blevel
.If you have access to MOSC, search for the blevel keyword, especially the subject Index Health. The Oracle Community was also suggesting rebuilding indexes for indexes have blevel more than or equal to 4.
Paul White♦57k1515 gold badges300300 silver badges474474 bronze badges
Barbaros ÖzhanBarbaros Özhan
You can find fragmented table using below query
And Use below for find fragmented Index.1. Execute below
Once above done you can get index analyze report in report from INDEX_STATS table using below query.
FROM INDEX_STATS;
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This INDEX_STATS table contain only 1 row. so to get multiple indexs report you have to run one by one and get report after each run.
Mominul OCP 10g 11gMominul OCP 10g 11g
Fragmentation in itself is not an issue. It's the extent of fragmentation that poses a threat. Fragmentations < 1% are no problem. There is lots of help on SO to generate list of Indexes by Table name and fragmentation in those indexes.
Shiv SidhuShiv Sidhu
Check Table Fragmentation Oracle Chart
Is there any way to check whether a table or index has been fragmented?
How to create an incognito shortcut specific website chrome. How to check if table is fragmented or not?
How to check if index is fragmented?
I searched Google but didn't get satisfactory answers. Some points like explain plan, table fragmentation, index rebuild etc I got. But what should be our first step and how should be resolve. How step by step we can move forward to resolve the issue?
Paul White♦57k1515 gold badges300300 silver badges474474 bronze badges
Onkar Tiwari
migrated from stackoverflow.comAug 31 '18 at 9:20
This question came from our site for professional and enthusiast programmers.
3 Answers
You need to use
INDEX_STATS
view to determine fragmentation. Firstly, You need to populate this view with an individual index by using :
and then look at these values
ratio
and height
:If ratio is more than %20
or height is more than or equal to 4
or lf_rows is lower than lf_blks,
then you need to rebuild your index against fragmentation.
The
blevel
column of dba_indexes
table is my main point of interest. This gives the number of branch levels (including the root node) for a b-tree index, and the column height
is closely related to blevel
.If you have access to MOSC, search for the blevel keyword, especially the subject Index Health. The Oracle Community was also suggesting rebuilding indexes for indexes have blevel more than or equal to 4.
Paul White♦57k1515 gold badges300300 silver badges474474 bronze badges
Barbaros ÖzhanBarbaros Özhan
You can find fragmented table using below query
Jan 11, 2012 Hi Scott, I am trying to move the bottom left and bottom right action bar via the /nui movers command. I am able to move both of the bars however my problem lies in that the player/party button and the infopanel button are actually docked to these bars and move with them. How to move action bars in wow around. You probably have your action bars locked. Look in the menu for UI settings Action bars unlock them if you want to move skills. Try holding SHIFT while moving. @SAndokan that is the correct answer, I was going to post it as an answer until I saw your comment. Feb 05, 2010 go to curse.com and search for bartender 4 it is an action bar replacement and u can move your action bars anyway u want and much more! Feb 11, 2011 Get something like MoveAnything or FluidFrames and it will take care of all of the above. They're all very simple blizzard UI component resizers/movers and they'll allow you to hide components too. Get something like MoveAnything or FluidFrames and it will take care of all of the above.
And Use below for find fragmented Index.1. Execute below
Once above done you can get index analyze report in report from INDEX_STATS table using below query.
FROM INDEX_STATS;
This INDEX_STATS table contain only 1 row. so to get multiple indexs report you have to run one by one and get report after each run.
Mominul OCP 10g 11gMominul OCP 10g 11g
Fragmentation in itself is not an issue. It's the extent of fragmentation that poses a threat. Fragmentations < 1% are no problem. There is lots of help on SO to generate list of Indexes by Table name and fragmentation in those indexes.
Shiv SidhuShiv Sidhu
I have a table which seems to be taking up more space than it needs to. I have been advised to copy the data to a new table and rename the new table and old table to swap them. How can I confirm if a current table is actually fragmented? How can I estimate or calculate the new size of the fresh table containing the same data?
Stuart WoodwardStuart Woodward99333 gold badges1313 silver badges2828 bronze badges
3 Answers
If your stats are up to date, this should give a decent indication if tables have lots more blocks than the volume of row data suggests.
This space would be used for future inserts, so isn't necessarily a problem. If you've done a large archive or delete of data, it may be worth reclaiming space (especially if you do lots of full table scans). [Note: I've assumed 8k blocks, which are the default.]
If you do a CREATE/DROP/RENAME you'll lose any indexes, constraints, grants (plus table comments if you use them).
You are better off checking the current tablespace (look in USER_SEGMENTS) and doing an
ALTER TABLE tablename MOVE current_tablespace;
You will need to rebuild indexes aftwards too. Pick them from USER_INDEXES and do an
Gary MyersGary MyersALTER INDEX .. REBUILD;
32.5k33 gold badges4141 silver badges6767 bronze badges
-- Try to run this script using svrmgrl connected as DBA
UltraCommitUltraCommit1,23755 gold badges3333 silver badges5555 bronze badges
Consider using
gpechegpechedbms_space.space_usage
and other procedures in the dbms_space
package.18.3k33 gold badges3030 silver badges4646 bronze badges