Between 10 and 12 million pilgrims are expected to visit the tomb of Sant Iago this Holy Year. Stripped of their backpacks walking pilgrims will have to jostle for a place in the cathedral with all other pilgrims. The restricted access to the Cathedral has been established not only for security purposes but also to limit the number of people in the Cathedral to 1,200 which has been estimated to be a "safe" maximum.
This info from Rosina:
The "Casa del Cabildo" is a refurbished building located in Platerias right between the Pilgrims' office and the stairs leading up to Quintana square; that is, in front of the fountain with the horses. That is where the backpacks will need to be left by those pilgrims wishing to enter the Cathedral.
Further, beginning on March 29, entrance to the Cathedral will only be possible through the door on Platerias and the holy Door (the Azabacheria and Obradeiro doors will only be used to exit the Cathedral and for official ceremonies). Pocketbooks and bags will be subjected to searches, and those beyond a modest size will have to be left in storage. Fortunately, the Casa del Cabildo is right in front of the entrance doors.
John XXIII is the name of the area where tour buses, and the like, park, and it is within easy walking distance from the Cathedral (right behind the Saint Francis church and convent); there will also be facilities for storing backpacks, etc., there. Lastly, if need be, additional storage facilities will be available at San Martin Penario which is on Azabacherias.
The whole storage project is being handled by the Archdiocese and a storage fee is yet to be decided upon, although, it has been assured, it will be a very small one.