cluster.split error

Hello I am trying to perform cluster.split command for 3857861 sequences. I am using 12 processors which is the maximum no.of processors in my server. After taking two days the job automatically gets killed. I know it is a RAM issue, but I was wondering why does a server that is currently performing only mothur gets jammed with all the memory usage and ultimately get kiled? Is it because of the size of the data. The command I used is below and I am following the MIseq SOP manual in the mothur website.

mothur > cluster.split(fasta=stability.trim.contigs.good.unique.good.filter.unique.precluster.pick.pick.fasta, count=stability.trim.contigs.good.unique.good.filter.unique.precluster.uchime.pick.pick.count_table,, splitmethod=classify, taxlevel=4, processors=12, cutoff=0.15)

Reducing the number of processors used will reduce the memory required.

Thanks- I had the same issue!