Hi Akriti,
It depends on the Hardware config of the system, also you may need to do performance tuning as suggested in following:
XML to Idoc- XML size more than 200 MB
Whats your PI version? Single Stack AAE is capable of handling / processing huge message size (but still depends on Hardware config)..refer following:
PI 7.3, Benchmarks for message size and throughput.
Regards,
Azhar