Tuesday, March 31, 2015

assumption is the mother of ....

We had complaint about a batch job that took much longer to complete on environment A then on environment B.

I checked and indeed the plans where different

As we recently updated from 11.2.0.4 BP12 to BP15 on that environment (A) my first idea was that this caused the issue,  to exclude everything I imported the table stats from the working environment B to the environment A.
Still I got the same plan.


I checked the system stats they were the same.
I used Mauro Pagano's excellent SQLd360 tool get it here and couldn't see anything (that's ENTIRELY my fault I could really work on this and was multitasking a lot due to other constraints;-).


I ran a 10053 optimizer trace and saw that there were fix controls not used on env B and only FTS were used in SINGLE TABLE ACCESS PATH , .... bizar 

Environment A

SINGLE TABLE ACCESS PATH 
  Single Table Cardinality Estimation for TABLE_X[TABLE_X
  Column (#2): 
    NewDensity:0.000210, OldDensity:0.000476 BktCnt:254, PopBktCnt:2, PopValCnt:1, NDV:4725
  Column (#2): COL2(
    AvgLen: 7 NDV: 4725 Nulls: 0 Density: 0.000210 Min: 113898 Max: 814396873
    Histogram: HtBal  #Bkts: 254  UncompBkts: 254  EndPtVals: 254
  Column (#3): 
    NewDensity:0.000019, OldDensity:0.001339 BktCnt:254, PopBktCnt:18, PopValCnt:9, NDV:48180
  Column (#3): COL3(
    AvgLen: 7 NDV: 48180 Nulls: 0 Density: 0.000019 Min: 113328 Max: 816880773
    Histogram: HtBal  #Bkts: 254  UncompBkts: 254  EndPtVals: 246

  Table: TABLE_X  Alias: TABLE_X
    Card: Original: 633107.000000  Rounded: 1  Computed: 0.00  Non Adjusted: 0.00
  Access Path: TableScan
    Cost:  1113.98  Resp: 1113.98  Degree: 0
      Cost_io: 1100.00  Cost_cpu: 180830851
      Resp_io: 1100.00  Resp_cpu: 180830851
  Best:: AccessPath: TableScan
         Cost: 1113.98  Degree: 1  Resp: 1113.98  Card: 0.00  Bytes: 0

While on the other env B

SINGLE TABLE ACCESS PATH 
  Single Table Cardinality Estimation for TABLE_X[TABLE_X
  Column (#2): 
    NewDensity:0.000210, OldDensity:0.000476 BktCnt:254, PopBktCnt:2, PopValCnt:1, NDV:4725
  Column (#2): COL2(
    AvgLen: 7 NDV: 4725 Nulls: 0 Density: 0.000210 Min: 113898 Max: 814396873
    Histogram: HtBal  #Bkts: 254  UncompBkts: 254  EndPtVals: 254
  Column (#3): 
    NewDensity:0.000019, OldDensity:0.001339 BktCnt:254, PopBktCnt:18, PopValCnt:9, NDV:48180
  Column (#3): COL3(
    AvgLen: 7 NDV: 48180 Nulls: 0 Density: 0.000019 Min: 113328 Max: 816880773
    Histogram: HtBal  #Bkts: 254  UncompBkts: 254  EndPtVals: 246
  ColGroup (#1, Index) IX_4
    Col#: 4 5    CorStregth: -1.00
  ColGroup Usage:: PredCnt: 2  Matches Full:  Partial: 
  Table: TABLE_X  Alias: TABLE_X
    Card: Original: 633107.000000  Rounded: 1  Computed: 0.00  Non Adjusted: 0.00
  Access Path: TableScan
    Cost:  1113.55  Resp: 1113.55  Degree: 0
      Cost_io: 1100.00  Cost_cpu: 180830851
      Resp_io: 1100.00  Resp_cpu: 180830851
  Access Path: index (AllEqRange)
    Index: IX_2
    resc_io: 9.00  resc_cpu: 69774
    ix_sel: 0.000019  ix_sel_with_filters: 0.000019 
    Cost: 9.01  Resp: 9.01  Degree: 1
  Access Path: index (AllEqRange)
    Index: IX_3
    resc_io: 28.00  resc_cpu: 257919
    ix_sel: 0.000210  ix_sel_with_filters: 0.000210 
    Cost: 28.02  Resp: 28.02  Degree: 1
  ****** trying bitmap/domain indexes ******
  Access Path: index (AllEqRange)
    Index: IX_2
    resc_io: 3.00  resc_cpu: 23964
    ix_sel: 0.000019  ix_sel_with_filters: 0.000019 
    Cost: 3.00  Resp: 3.00  Degree: 0
  Access Path: index (AllEqRange)
    Index: IX_3
    resc_io: 3.00  resc_cpu: 47964
    ix_sel: 0.000210  ix_sel_with_filters: 0.000210 
    Cost: 3.00  Resp: 3.00  Degree: 0
  Bitmap nodes:
    Used IX_2
      Cost = 3.001919, sel = 0.000019
    Used IX_3j
      Cost = 3.004938, sel = 0.000210
  Access path: Bitmap index - accepted
    Cost: 6.007407 Cost_io: 6.000536 Cost_cpu: 91721.496173 Sel: 0.000000
    Not Believed to be index-only
  ****** finished trying bitmap/domain indexes ******
******** Begin index join costing ********
  Access Path: index (FullScan)
    Index: IX_1
    resc_io: 1439.00  resc_cpu: 136869152
    ix_sel: 1.000000  ix_sel_with_filters: 1.000000 
    Cost: 1449.25  Resp: 1449.25  Degree: 0



Being in a hurry because I was busy with plenty of stuff  I assumed  that fix_control was the problem

however setting fix_control didn't change a thing so I went back to check  the trace with a colleague  and then we saw following


Table Stats::
  Table: TABLE_X  Alias: TABLE_X
    #Rows: 633107  #Blks:  4056  AvgRowLen:  43.00  ChainCnt:  0.00
Index Stats::
  Index: IX_1  Col#: 1
    LVLS: 2  #LB: 1437  #DK: 633107  LB/K: 1.00  DB/K: 1.00  CLUF: 37633.00
  Index: IX_2  Col#: 3
    LVLS: 2  #LB: 1665  #DK: 48180  LB/K: 1.00  DB/K: 5.00  CLUF: 287723.00
    INVISIBLE
  Index: IX_3  Col#: 2
    LVLS: 2  #LB: 2103  #DK: 4725  LB/K: 1.00  DB/K: 25.00  CLUF: 118278.00
    INVISIBLE
  Index: IX_4  Col#: 4 5
    LVLS: 2  #LB: 2490  #DK: 14906  LB/K: 1.00  DB/K: 2.00  CLUF: 36217.00
    INVISIBLE



We checked the status of the indexes they were INVISIBLE, when they were put back to VISIBLE the correct plan was choosen again ...


Moral of the story : As one of my previous managers (probably the best I had so far but that is another story )said Assumption is the mother of all f*ck ups, don't think that everything is a complicated problem and check basic things, and take your time to check things don't do 50 things at the same time, man anyway can't multitask ;-------------)
luckily in the end it didn't take to much time to identify the issue...



Thanks @MartinDBA, @Mautro and everyone interacting in the discussion on twitter


Saturday, March 14, 2015

wow what a seminar

wow it’s behind us again a great OUGN Varseminar 2015,big shout out to the boa(r)(t)d  to have made this again a success. 


You’ve set the bar very high for coming years, I hope to be able to be part of other future editions  ! 
It was a very good idea to put the exhibition hall not on the same floor as the talks,giving more breathing room around the rooms

Apart from the fact that a seminar on a boat creates a special bond with the people aboard the quality of the talks was really very good, i learned plenty of things...

I really enjoyed being on a boat with people passionate about there job in fact for most of the people it more then just being a job it is a passion , vocation ,...

It was great to meetup with old friends and make new ones

my personal highlights not in any particular order

were the sessions of :

Neil Johnson (@neiljdba) about contentious small tables really a very good presentation I learned a lot about the hakan factor, I strongly recommend to go to follow this session on other conferences this year, beside that Neil is a great guy to hangout with. Unfortunately I missed his talk about jumbo frames...but the good news I found his slides already ;)

Kellyn Potvin-Gorman  also known as @DBAKevlar talking about AWR Warehouse thanks to her presentation I finally know that this is a “free” limited license if you have licensed tuning and diagnostic pack for your  databases, I will start pushing for it at my current customer,because it can really save you bacon and lots of discussio. Her talk about EM 12c was also great by the way despite that she was pretty i'll suffering from her sinusses, so really well done

Jan Karremans’ session ‘ok now my database crashed’ was a very good reminder on how important it is to take this part of your oracle installation not too lightly, btw Jan is pretty (hyper) active on twitter ;-) here (@johnnyq72)

James Morle’s (@JamesMorle) session about opitmizing table scanning  and how to tune all layers of the cake even the blue ones

Luis Marques (@drune) session about Rat was of a very high quality so was his talk about Resource Manager, this is a subject that needs bigger attention especially in the actual spirit of consolidation

I really enjoyed the ‘Instructor’ aka Uwe Hesse’s presentations about the broker and fra I envy his courage of doing a complete talk with live demo’s. (@UweHesse)

I had a blast doing the SE Round Table BE (boat edition) with SE lady Ann Sjokvist (@annsjokvist) and my good friend Jan Karremans, I liked the chemistry that was going on on stage.
SE edition can be a good solution for you, it depends on your business needs and it is an easy step up to EE when you later would need those features. Each of us three looked the product from a Different angle 
Ann really has lots of experience with it and is a really advocate, Jan Looked at it from the business side, and I for my part I am a spoiled EE dba who realises that you need to do correct size matching and see if the 

I had my own talk about a great underestimated product in the engineered systems line up the Sparc Super Cluster, I’ve been working with this product since beginning 2014 and it is for me very much the Swiss Army knife of the engineered exadata systems, providing an un-paralleled versatility and flexibility. 
I liked the questions and discussion with Jacco Landlust that came offline after my talk about Super Cluster.

I would like to explicitely thank Oyvind Isene (@OyvindIsene) and Kjell Tore for many of us international speakers you guys are the public face of OUGN. Speaking For myself if I wouldn’t have come to OUGN as a delegate in 2013 after talking to Oyvind at #OOW2012  I wouldn’t be speaking now, so Oyvind  I owe you  a lot. I hope the next board will continue your work and the investments of blood sweat and tears you two did.

I would also like to thank portrix Florian , Connie and Bjoern (@brost)for the great gin / buffet you organised in Kiel. It becomes clearly a tradition.

Too bad I missed several sessions I due to overlap ;-(


Nice meeting you all girls and guys

Thank you 

Jan Karremans
Heli Helskyaho ;-)
Debra Lilley
Brendan Tierney
Oyvind Isene
Kjell Tore
Frits Hoogland
Christian Antognini
Neil Johnson
Kellyn & Tim Gorman
Gurcan Orhan
Bjoern Roest Florian 
Andy Colvin & wife
James Morle
Luis Marquis
Kelly Potvin
Tim Gorman
Jacco Landlust
Alex Nuijten
Patrick Barrel
Magnus Fagertun
Mark Rittman
Eric Van Roon



Thank you all for making my OUGN 15 so great

If you haven't decided yet maybe this small video and some pictures (sorry I am not so good with an iphone DSLR user) can persuade you to attend or submit for OUGN16


video