MySQL Error Occurred

Error Message:
1: Can't create/write to file '/tmp/MYa2t4lb' (Errcode: 30)

SQL:
SELECT I.name, I.productId FROM CubeCart_inventory AS I, CubeCart_category AS C WHERE C.cat_id = I.cat_id AND I.cat_id > 0 AND I.disabled = '0' AND (C.cat_desc != '##HIDDEN##' OR C.cat_desc IS NULL) ORDER BY I.popularity DESC