Error: limitcheck

I created postscript program to read and generate PDFD from line data stream

the PS routine just read the file from line one till the end , format and output the line .

It works well with file with 1000 up to 4,000  and suddenly when I encounter large file - up to 20,000 pages I had this error by distiller

Error: limitcheck; OffendingCommand: def

def  is the postscript part used as /VAR  xxx def    etc

So it is built in PS command.

Why suddenly it is not accepted !!

I split the large  files into two files and both ripped correct and the PDF generated by distiller.

I touhgt it is memory problem but I jhave 4 GB of ram!! and perhaps some internal memory allocation of PS !!!

Regards

Dr. Adam.