CCTM output file is limited to 4GB

Hi everyone.

Currently I am using CMAQ 5.3, the resulting file from my cctm is limited to 4gb.
How to remove this limit, please guide.

Thanks you.

Whici I/O API version and netCDF version are you using? In your script, do


(this is the default for I/O API 3.2 with netCDF 3.6.2 or later)

Hi cjcoats.
I use I/O API 3.2 and netCDF 4.7.
In my script have IOAPI_OFFSET_64 YES.

I’ve got along fine with files as large as 1.2 TB (33-year LSM/hydrology runs, and that with I/O API 3.1, where I needed an explicit IOAPI_OFFSET_64 YES)…

Wait a minute… is an individual timestep total volume that large? For that, you need to compile everthing (CMAQ + I/O API) with the “medium” memory model (see, and to be using netCDF-4

With my netCDF and WRF, I tested the big file and it was successful.