FULL hint usage

Hi,
I would like to know the benefits of using FULL table scan hint.
SELECT /*+ FULL(A) */ * FROM TEST A;
In our production system, when we join two bulk tables using FULL hint and it has got indexes on the join fields,
performance is much better.
If indexes are dropped and FULL hint is removed, performance is pretty slow.
However, when indexes are available and I use FULL hint, how we get this performance improvement, does the processing
happens in memory itself, please share your views on this.
Regards,
Sarathy

Can you post your queries and EXPLAIN PLAN output? Otherwise we cannot be of much help.
Make sure you post using the [pre] and [/pre] tags to format the output.
cheers,
Anthony

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Explicitly using full hint

Hi
In some of codes, I see the DBA explicitly force the sql to perform a full table scan by using full hint. What should be the reason?
thanks

user8779435 wrote:
I know Anurag. But what could be the reason for DBA to believe on that ...By comparing the one with without full hint and one with full hint.
If he would be getting better response time or less consistent gets or any other stats that he fill is better for the plan.
Like sometime doing full table scan would make a query to do hash join rather than nested loop and it could be possible that full table scan with hash join is giving better stats then index scan with nested loop
Regards
Anurag

Reg: Exadata and /*+ FULL */ hint -

Hi Experts,
Recently, our database got migrated to Exadata environment, and a DBA told me that using the /*+ FULL */ hint in the query increases the query performance.
Doubt -
1) Does it actually enhance performance?
2) I read some articles and got some information that Exadata does some kind of "Smart Scan" and "Cell Offloading" which makes the query efficient. But how does FULL hint contribute here?
This links talks something about this, but not sure if correct - Some Hints for Exadata SQL Tuning - Part III - SQL Optimizer for Oracle - SQL Optimizer for Oracle - Toad World
Please share your thoughts and advise.
Thanks and Regards,
-- Ranit
( on Oracle 11.2.0.3.0 - Exadata )

Ranit -
Lots of good advice given by others. A little more to add to the comments already made...
Using a full hint as a general tuning rule on Exadata would not be a good idea, just like the sometimes proposed notion of dropping all indexes on Exadata to performance is not a good idea. As Mohamed mentions, a key performance optimization for Exadata are the smart scans, which do require direct path reads. Pushing for smart scans is what drives these types of ideas; because, other than the index fast full scan, index scans will not smart scan. However, smart scanning isn't always faster. OLTP type queries that are looking for one or two rows out of many are still usually faster with an index even on Exadata. If you find using a hint like FULL does improve a query's performance, then just as with using hints in general, it's better to determine why the optimizer is not picking the better execution plan, a full table scan in this case, in the first place; and resolve the underlying issue.
What you will probably find is you are over-indexed on Exadata. If you have control of the indexes in your environment, test by making certain indexes invisible and seeing if that helps performance. Indexes that were created to eliminate a percentage, even a large percentage, of rows, but not almost all rows for queries are candidates to be dropped. You definitely want to tune for direct path reads.
This is done by doing index evaluations as described; making sure your stats are accurate and up-to-date; as mentioned by Franck, be sure to gather the Exadata system stats - as this is the only thing that helps the optimizer be Exadata aware. And also, especially if you are running a data warehouse workload, you can look into using parallelism. Running queries in parallel, often even with a degree as little as 2, will help prompt the optimizer to favor direct path reads. Parallelism does need to be kept in check. Look into using the DBRM to help control parallelism - possibly even enabling parallel statement queuing.
Hopefully these will give you some ideas of things to look at as you enter the realm of SQL Tuning on Exadata.
Good luck!
-Kasey

Time since last full charge - Usage & Standby Keeps Resetting

When I normally charge my iPhone 3GS to roughly into the 90s (percentage), the Usage & Standby times under "Time since last full charge" both reset. I do not go to 100% charge. I only do that like once every few weeks.
I know that these times were buggy sometimes in 2.X versions of the OS where the times would read "--". Usually discharging the battery completely & recharging would fix that, although temporarily...
Anyone else?

Apple does not make your phone battery go to 100% each time you charge. In every laptop or cell phone battery there is a finite amount of times that you can charge your phone up to 100%. After a certain amount of times the battery will die. So Apple charges up to 90% (or something like this) so you won't have to worry about a battery replacement. According to a post I read on engadget.com a normal iPhone user would have to worry about charging their iPhone battery once every 5 years with the way Apple charges your iPhone.
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Syncing uses full cpu usage

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Windows 7! Oh joy.
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FMS stuck on full CPU usage

Hi,
We are hosting a FMS3 server on a Redhat EL5. The Redhat EL5
is fully patched with Red Hat Network, and the version on the FMS
server is FMS3_0_2_r217. We are running the server a few months
without any problems so far. There are about 30 vhosts active on
the server.
Today the load of the server increased by a lot, and we saw a
process called 'fmscore' taking all CPU power (200%). When I
restarted the server, the problem returned. When I went to the logs
folder I saw the following entries:
-rw-rw---- 1 3188489 Oct 17 11:31 core.00.log
-rw-rw---- 1 10487959 Oct 17 11:30 core.01.log
-rw-rw---- 1 10487978 Oct 17 11:30 core.02.log
-rw-rw---- 1 10486128 Oct 17 11:29 core.03.log
-rw-rw---- 1 10520479 Oct 17 11:11 core.04.log
-rw-rw---- 1 10505753 Oct 17 11:11 core.05.log
You notice the time-stamps are within minutes from each
other, and each logfile is 10mb in size. When I opened the logfile,
I got the following messages:
2008-10-17 11:30:15 9407 (e)2581279 Assert failed in
/FlashPlayer6_02_FlashCom/shared_tcserver/tcparser.cpp line 109 -
2008-10-17 11:30:15 9407 (e)2581279 Assert failed in
/FlashPlayer6_02_FlashCom/shared_tcserver/tcparser.cpp line 109 -
2008-10-17 11:30:15 9407 (e)2581279 Assert failed in
/FlashPlayer6_02_FlashCom/shared_tcserver/tcparser.cpp line 109 -
2008-10-17 11:30:15 9407 (e)2581279 Assert failed in
/FlashPlayer6_02_FlashCom/shared_tcserver/tcparser.cpp line 109 -
This was set about 1000 times per second.
Does anyone know what can be the cause of this behavior, and
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Cheers
Nstuff

Bad data is that which cannot be parsed because it is not in
the expected format.
When using an "Arraycollection" this message could be
produced by incorrectly mixing AMF0 with AMF3 data types; I would
check this first. Another reason for this message is that a
variable exceeds the memory limit imposed on the data type.
Try to identify a minimal test case and report back with what
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Why does DAQ cause full CPU usage?

i have set up my vi to acquire a buffer of 360 data points, it acquires one point every time there is a pulse on an external channel. however whilst it is waiting for all the points it uses 100% cpu. can i stop it doing this?
Attachments:
set_up_acquire.vi ‏95 KB

Hello,
The short answer is yes. You can keep it from using 100% CPU while waiting for points. I took a look at your code. One approach would be to put AI Read.vi in a loop, read a portion of your data at a time, then accumulate all the data at the end. A way to accomplish this would be to set "number of scans to read" input of AI Read.vi to zero, watch the "scan backlog" output, then do an actual read when the backlog has the number of scans you want. This allows the program to sleep between reads. Be sure to put a small wait in the read loop.
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Google Chrome CPU usage almost 100%

Hey guys,
so I recently updated from Snow Leopard directly to Mountain Lion and now I have a issue I can't fix by myself.
I'm using a Macbook Pro Mid 2010, 4gig Ram, 2,4 Intel Dualcore, GT 320M - now running OSX 10.8.3
I've got a 27" secondary display, where I usually enjoy my content Youtube e.g.. It used to work very fluently with no probs at all.
I could run a Skype conv., a Youtube vid, eyeTV and various apps simultaneously without any performance issues.
NOW: I have no other app running but Chrome, open up any random youtube-video and it starts to lag within seconds. When I switch to my 27" screen it shows a CPU usage of around 100% for Chrome and 80% for Pepperflashplayer, going down to 80%; 70% when displaying on my macbook screen.
I've read that RAM upgrade might be recommended for running Lion or ML on "older" macbooks. However during this lags and CPU peaks I still have around 1,5gig of free RAM. I've already installed 'Memory Clean' to monitor my RAM usage and keep it at a certain level.
This happens using      Chrome: Pepperflashplayer + Chrome
                                  Firefox: Shockwaveflash + Firefox
                                   Safari: Flashplayer + Safari
     always having almost full cpu usage and extreme graphic lags.
This does not happen when displaying HD content from my hard drive, eyetv and such.
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Hi,
Does this problem occur on another machine or only this
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How to give a hint on a table within a view

How do I give a FULL hint to a table within a view?
The table that I want to give a hint on resides in a different schema that I am working in. So, when I give the following hint, Oracle just sits on it and does nothing (I am afraid I can't do the same, so please help).
/*+ FULL (VW.SCHEMA_NAME.TABLE) */

Hi,
In the hints documentation you have to pre cursor the table with the name of the view such as for example.
/*+ full(view_name.table_name) */
this is called a global table hint. Here is the link for your reading, it has an excellent example
http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14211/hintsref.htm#i27644
and this one lists all the hints available to use.
http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14211/hintsref.htm
enjoy.
al

Global Hints in oracle

Hi all,
Can any one please tell me what is Global Hints in oracle.
i know normal hints usage.
what is difference between normal hints and global hints.
Thanks in Advance,
Sanjeev.

http://download.oracle.com/docs/cd/E11882_01/server.112/e16638/hintsref.htm#PFGRF50104

Doubts in tuning Hint - ORDERED & APPEND

Hi,
Can you clear my doubts regarding ORDERED and APPEND hints usage in query for tuning?
Give some sample sql scripts if at all possible
Thanks in advance.

HI,
the hints have very different scopes.
The APPEND hint is used to write a table in "direct mode", bypassing any check over the object freelists and writing directly after the high water mark. This, in an uncontrolled environement, may leave te object to groove unless fullfills the tablespace.
The ORDERED hint is instead used to "drive" the optimizer and tell it to join the the object in the same ordered as the appears in the FROM clause. The most important thing to check, using that hint, is that the "logical" join order is respected 'cause if not MERGE JOIN CARTESIAN operation may be choosen as access paths.
Hope this helps
Max

KDE4 ignores font hinting settings [solved: qt bug, fixed in 4.5]

Full hinting enabled in Gnome and KDE:
Slight hinting enabled in Gnome and KDE:
KDE seems to ignore the hinting settings. It's present in ~/.fonts.conf, also Qt3 apps work fine.
I would like to use slight hinting everywhere, but KDE4 defaults to full hinting anyway
Google wasn't very helpful on this issue, and I found no mention of it in the KDE bugzilla.
Last edited by eWoud (2008-10-05 10:34:21)

Edit2: Oops, ignore my patch - it doesn't work. Qt4 doesn't even use cairo.
Last edited by brebs (2008-10-10 02:24:04)

Using Hint in Update or Select Statement...

Hi ,
I had an update statement that will get the data from the inline select statement,now where can i can keep the hint ,either in update statement or in Select statement...
Please let me know if my sample script is wrong or any better way to approach...Please assume that Salary table had millions of employee's salary records.
update emp
set salary = salary + (select /*+ full(a) parallel(a,4) */ salary from Salary
where experience > 5 and empno = 55 )
where empno = 85Thanks
Rede

The better approach would be to determine why you need a hint in the first place. If you're using a hint, that implies that the optimizer is choosing the incorrect plan when left to its own devices. That, in turn, implies that the statistics on your objects, the statistics on your system, your optimizer parameters, your session's optimizer settings or some other variable is incorrect. You're generally better off fixing the root problem than hinting every query.
In this specific case, the parallel hint is invalid because there is no table aliased A. The full hint is invalid for similar reasons. Plus, with the query you provided, if A was intended to be the SALARY table, it seems exceptionally unlikely that you really want to do a full scan on the salary table to look for what had better be a single row (otherwise your query would throw a "too many rows returned" exception).
Justin

Missing usage stats on 4S

Not sure what happened here. I've never had any kind of problem with the 4S battery usage at all, but suddenly yesterday, my usage stats (Time since last full charge: Usage & Standby) just disappeared. They were there - I used to check them periodically just to make sure the phone was ok, but as I said, they just vanished!
The phone's working just fine but I'd like the stats to work.
I've resisted the temptation to update to 5.01 so far as I'm not sure if this would fix the problem or just create new ones!
Can anyone suggest anything at all?

OK, now solved.
I just charged till I saw the plug icon in the corner, removed the connector and put it back again. It charged again for a minuite or so and then the plug icon appeared again. At this point I just re-booted and the stats appeared immediately.
I guess the phone was not 100% charged the first time the plug icon appeared and these stats only appear after the phone has been 100% charged.

Oracle hints

Hi,
I want to know if it's possible to avoid using an index in a query.
For example I defined 3 column indexes on a table named "SUMMARY_VECTOR" with the following names respectively:
1-SUMMARY_VECTOR_ENTITY_NAME_IDX
2-SUMMARY_VECTOR_IDX_CASE_NAME
3-SUMMARY_VECTOR_VECTOR_ID_IDX
I want to know if I can avoid using one of the three indexes in my query by using oracle hints.
If it's possible, please if can u post an example
Thanks

but I have other procedures which are affected by this new created index.Interesting, why didn't you try to understand this fact ?
HINT usage shouldn't be taken lightly. You are saying to Oracle optimizer you know better the route to be taken regardless what is happening to your table and regardless your stats.
HINT is a fixed advise, and doesn't change with the table data and statistics.
Maybe today it is bad to use the index, but tomorrow, after thousands inserted rows in your table, that would be better, unfortunately, your hint will ignore it.
Before going into HINT usage, you should understand why this index sounds bad for the other query, and if it's really bad, you should understand why Oracle wants to use it.
Nicolas.

FULL hint usage

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