Make the index that you wish to build unavailable to queries (READ access). This is done using SetMapSelectability(). This makes the index unavailable for use by the Query Optimizer. This operation should be performed both when rebuilding an existing index and when creating a new index. For example:

 
WRITE $SYSTEM.SQL.SetMapSelectability("Sample.MyStudents","StudentNameIDX",0)

Try %ignoreindices * perheps you have a problem with the indices
If you get an result you must rebuild the indices.

select vet.ID, svp.ID_PACIENTE, vet.conselho, vet.uf, vet.numConselho, vet.nome, svp.SEQ_SOLICITANTE, vet.numConselho , vlab.numConselho

from %ignoreindices * RPE.Veterinario vet

inner join RPE.VeterinarioLab vlab     ON vet.conselho = vlab.conselho    
AND vet.numConselho = vlab.numConselho   
AND vet.uf = vlab.uf
left join MySevi.SolicitanteVeterinarioPaciente svp     on svp.ID_VETERINARIO = vet.ID where svp.ID_PACIENTE in ('6408||284144||47633', '6408||284145||47634')