====== Database tags (CondDB and DDDb) ======
Data is produced or processed with different database tags. For example if the VELO was open, the database tag needs to specify that. 
===== Find the correct tags for your data =====
Look at your datafiles from the bookkeeping: the file names contain the dataset number. 
For the following datafile the dataset number is 5630. 
<code>
DATAFILE='LFN:/lhcb/MC/MC09/DST/00005630/0000/00005630_00000001_1.dst
</code>

To look up the tags log in to lxplus (you need a Grid Certificate to do this):
<code>
SetupProject LHCbDirac
dirac-bookkeeping-production-informations <datasetNumber>
</code>
for example:
<code>
dirac-bookkeeping-production-informations 5630
</code>

This produces the output:
<code>
Production Info: 
    Configuration Name: MC
    Configuration Version: MC09
    Event type: 30000000
Step0:Gauss-v37r5
      Option files: $APPCONFIGOPTS/Gauss/MC09-b450GeV-md100-nu1.py;$APPCONFIGOPTS/Conditions/MC09-20090602-vo-md100.py;$DECFILESROOT/options/30000000.opts;$LBPYTHIAROOT/options/Pythia.opts
      DDDb: MC09-20090602
      ConDDb: sim-20090402-vo-md100
Step1:Boole-v19r7
      Option files: $APPCONFIGOPTS/Boole/MC09-WithTruth.py;$APPCONFIGOPTS/Conditions/MC09-20090602-vo-md100.py
      DDDb: MC09-20090602
      ConDDb: sim-20090402-vo-md100
Step2:Brunel-v35r7
      Option files: $APPCONFIGOPTS/Brunel/MC09-WithTruth.py;$APPCONFIGOPTS/Conditions/MC09-20090602-vo-md100.py;$APPCONFIGOPTS/Brunel/veloOpen.py
      DDDb: MC09-20090602
      ConDDb: sim-20090402-vo-md100
Step3:LHCb-v28r0
      Option files: $STDOPTS/PoolCopy.opts
      DDDb: MC09-20090602
      ConDDb: sim-20090402-vo-md100
Number of Steps   1
Total number of files: 2
         LOG:1
         DST:1
Number of events [('DST', 53453)]
Path:  /MC/MC09/Beam450GeV-VeloOpen-MagDown-Nu1/MC09-Brunelv35-withTruth/None
/MC/MC09/Beam450GeV-VeloOpen-MagDown-Nu1/MC09-Brunelv35-withTruth/None/DST
</code>
Under the different steps you find the DDDb tags and the ConDDb tags, i.e. 'DDDb: MC09-20090602', 'ConDDb: sim-20090402-vo-md100' for the example file.


=== What if the tag returned is None? ===
It can happen, that the info reported by ''dirac-bookkeeping-production-informations'' 
lists ''None'' as database tags:
<code>
Production Info: 
    Configuration Name: MC
    Configuration Version: MC11a
    Event type: 11144103
-----------------------
 StepName: Merge12 for MC11 
    ApplicationName    : LHCb
    ApplicationVersion : v33r1
    OptionFiles        : $APPCONFIGOPTS/Merging/CopyDST.py
    DDB                : None
    CONDDB             : None
    ExtraPackages      : AppConfig.v3r118
-----------------------
</code>

In this case the production information got lost while merging. 
You can have a look at the database tags used for the merge job and hope they where correct
<code>
SetupGauss
cat $GAUSSROOT/options/Gauss-MC11a.py
</code>
===== Implement the tags in your options file =====
When using real data, you need a DDDB tag (DDDB) and a CondDB (LHCBCOND) tag. 

Insert the following lines to your options file:
<code>
DaVinci().CondDBtag = "head-20091211"
DaVinci().DDDBtag = "head-20091120"
</code>
When running over Monte Carlo data, you need a DDDB tag (DDDB) and a CondDB (SIMCOND) tag.
<code>
DaVinci().CondDBtag = "sim-20090402-vo-md100"
DaVinci().DDDBtag = "MC09-20090602"
</code>
  *Note: There is nothing like "DaVinci().SimCond", the corresponding information has to be written in the "CondDBtag".
  *It may sometimes be necessary to access the OracleDB. This can be achieved the following way:
<code>
from Configurables import CondDB
CondDB(UseOracle = True)
</code>

===== Using dictionaries =====
You can find a file including dictionaries of all yet known (and at least often used) tags under: "/afs/cern.ch/user/e/elsasser/public/dbtags/tagdict.py"
which can be imported to be used in a python script.
The base file is located under "/afs/cern.ch/user/e/elsasser/public/dbtags/prodFileList.txt"

===== Check if the correct tags were used in your job =====
Look at the stdout file of your job:
After the start of Loki you will find something like the following statements:
<code>
DDDB                 INFO Connected to database "sqlite_file:/afs/cern.ch/project/gd/apps/lhcb/lib/lhcb/DBASE/Det/SQLDDDB/v5r17/db/DDDB.db/DDDB"
DDDB                 INFO Using TAG "MC09-20090602"
SIMCOND              INFO Connected to database "sqlite_file:/afs/cern.ch/project/gd/apps/lhcb/lib/lhcb/DBASE/Det/SQLDDDB/v5r17/db/SIMCOND.db/SIMCOND"
SIMCOND              INFO Using TAG "MC09-20090402-vc-md100"
</code>
===== Where to find information about global tags =====
Follow this link: http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/dbase/conddb/release_notes.xml

===== More =====
[[https://twiki.cern.ch/twiki/bin/view/LHCb/RecommendedTags#Where_do_I_find_information_abou | "Recommended Tags" Page in TWiki]]