This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.
Hi Stephen, > As I have problems with writing a moderate size netcdf file, I decided > to try one of your examples. it is pres_temp_4D_wr.f90. I compile this > code on our aix power 6 machine and for the parameter settings you > provide with the code there is no problem. The problem start if I > increase the dimensions of the arrays to something more interesting: in > my case nlats 300, nlons 300 and nlvls 1738. This causes a core > dump. Hmmm, I just tried this and it worked fine, writing a netCDF "classic" format file of about 2.5 Gbytes: -rw-r--r-- 1 russ ustaff 2502722808 Jun 30 14:39 ptw.nc You should be able to write such a file with no special flags from any version of netCDF since about 3.5.1. Check the possible causes in the answer to this FAQ: Why do I get an error message when I try to create a file larger than 2 GiB with the new library? http://www.unidata.ucar.edu/netcdf/docs/faq.html#Large%20File%20Support12 You don't need a 64-bit library (or a 64-bit computer) in order to write larger (netCDF 64-bit offset) files, as explained here: http://www.unidata.ucar.edu/netcdf/docs/faq.html#Large%20File%20Support7 So you should be able to create even larger files using the 64-bit offset format by using the correct creation mode in the call to nf90_create, as in: ! Create the file. call check( nf90_create(FILE_NAME, or(nf90_noclobber,nf90_64bit_offset), ncid) ) > No special compilation flags (so on our machine xlf90 as I use the ibm > compiler) however, in order to make use of max.ram i edit the loader > file /usr/ccs/bin/ldedit -bmaxdata:0x60000000 name.of.executable You should not need larger RAM, but you have to have a file system that supports large files, as explained in the first FAQ above. > The question I have is do I hit a limit within netcdf itself. > > to my knowledge we are running a standard netcdf library (so not the > one for 64 bit). Do you know what version library you have? If it's pre-3.6 (about Feb 2005), there were some problems with large file support that were fixed in later releases. --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: XRV-955693 Department: Support netCDF Priority: Normal Status: Closed