# A Brief introduction

OCDB stands for Offline Condition Database and it contains both the detector configuration (e.g.: included HS in the daq, dead pixels, etc.) and the chip configration in the PIT (such as noisy FastOr, etc.).

The OCDB is a folder which can be found either in any AliRoot distribution (trunk, revision, release) under the path : $ALICE_ROOT/OCDB or in the alien catalogue under the path /alice/data/20xx/OCDB. The aliroot ocdb folder is located in : •$ALICE_ROOT/OCDB in any AliRoot distribution
• /alice/data/20xx/OCDB on alien (xx stands for 09, 10 or 11 depending on the data taking year) and it is used for RAW data reconstruction
• /alice/simulation/2008/4-15-Release/Residual (or Ideal/ or Full/ depending on the level of the detector miscalibration) for simulations

Inside the folder there are two subfolder which are relevant for SPD and they are ITS/Calib or TRIGGER/SPD. The former contains the detector configuration, whereas the latter the PIT configuration.

The detector OCDB folder structure is the following :

• SPDDead : Contains the information on the active HS. The container structure is at the level of pixels (grouped in chips and eventually in HS).
• SPDSparseDead : Contains the information on the dead pixels in the ACTIVE HS. The container structure is at the level of pixels.
• SPDNoisy : Contains the information on the noisy pixels during data taking. The container structure is at the level of pixels.
• SPDFOEfficiency : Contains the information of the FastOr response of the chips. The container structure is at the level of columns.
• SPDFONoise : Contains the information of the FastOr noisiness of the chips. The container structure is at the level of columns.

whereas the PIT OCDB object structure is quite simple since it contains only one folder : OCDB/TRIGGER/PITConditions

The fundamental objects are : SPDDead, SPDSparseDead, SPDNoisy, PITConditions. The other ones have been introduced before the data taking and at the moment only default values are used. ALL THE SPD OCDB OBJECTS ARE APPLIED ONLY AT THE RECONSTRUCTION LEVEL (the SPD is simulated as in its ideal configuration, that is ALL ALIVE).

The main 4 objects are handled by a class called AliITSOnlineCalibrationSPDhandler : it reads the objects, provides some information and writes the object wherever needed (apart from alien).

For a quick usage, please open the aliroot prompt. The handler class needs a run number and the ocdb folder locaiton as an input, therefore let's consider a run number 123456 and the ocdb aliroot default location.

A simple example is than   :

root [0] AliITSOnlineCalibrationSPDhandler *h = new AliITSOnlineCalibrationSPDhandler()
I-AliCDBManager::Init: AliEn classes enabled in Root. AliCDBGrid factory registered.
W-AliCDBManager::Get: Run number explicitly set in query: CDB cache temporarily disabled!
(Bool_t)1
root [2] h->PrintEqSummary()
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Eq summary:
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