CDO

1: Are cat and mergetime functionally equivalent? Speed differences?

2: cat can be used with ymonmin but fails with cdo ymonpctl,90 -cat infile* minfile maxfile outfie (3 input streams required error)
However, a two step process works
cdo cat infile* bigfile
cdo ymonpctl,90 bigfile minfile maxfile outfile

(same error with mergetime btw)

Thanks