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>From: "maseland j.e.j." <address@hidden> >Subject: netCDF offset limitations >Organization: National Aerospace Lab. NLR >Keywords: 200011291622.eATGMro00850 netCDF 3.4 size offset limitations Hi Hans, > we encounter read errors for netCDF Version 3.4 files larger than 2.1 > Gbyte for SUPER UX-10.2. We are aware of the offset limitations for > netCDF file containing fixed length variables. However the formulation > of the limitations is in my view ambiguous: > > "On systems that support very large files (exceeding 2 Gbytes), such as > IRIX 6.x or SunOS 5.6 with the large file compilation environment, it > is possible to create and access very large netCDF files with version > 3.4. The remaining size constraints are that the file offset to the > beginning of the record variables (if any) must be less than 2 Gbytes, > and the relative offset to the start of each fixed length variable or > each record variable within a record must be less than 2 Gbytes." > > My confusion originates from the word "relative". Does relative mean here > with respect to the start of the previous date part (visualised as > method 1). > Or is the offset to the position of the start of fixed-size data > part computed relative to the header (visualised as method 2)? > > Method 1: Method 2: > --------------- ------------- > --->| header | | header |<--------- > | --------------- ------------- | | | > --->| | | |<-- | | > | | data1 | | data1 | | | > | | | | | | | > | --------------- ------------- | | > --->| | | |<----- | > | | data2 | | data2 | | > | | | | | | > | --------------- ------------- | > --->| | | |<--------- > | data3 | | data3 | > | | | | > --------------- ------------- > In case of method 1, the offset value for each fixed size variable > must be smaller than 2.1 Gbyte. > In case of method 2, the offset value for the last fixed size variable > must be smaller than 2.1 Gbtye. > > To which method is referred to in your text? Method 2 was the intended interpretation. Sorry for the confusion, I'll try to make this clearer in the next revision. I wish it were easy to remove this limitation, but it requires a change to the format, which for netCDF would be a very big change. --Russ _____________________________________________________________________ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu