This document proposes adding compression to the netcdf-3 (aka classic) file format. The proposal has numerous limitations because of the nature of the existing netcdf-3 format.

The algorithm and data format proposed here requires re-writing an existing netcdf-3 file to move it to the new format. In effect, the re-written file becomes archival (read-only).

This document proposes an architecture for implementing thread-safe access to the netcdf-c library. Here, the term "thread-safe" means that multiple threads can access the netcdf-c library safely (i.e. without interference or deadlock or race conditions). This does not mean that the library is itself multi-threaded. Rather, access to the library is serialized so that only one thread at a time is executing the library code.

It appears to be the case that all current tests in the netcdf-c source tree are integration tests. That is they only access the library using calls to the externally visible API.

The DAP4 code testing is different in that it includes (for the first time) unit tests. These tests reference code that is considered internal to the library. For the library generated under autoconf, this is not a problem because those symbols are visible in the library: nothing is hidden.

The issue of multi-threaded read and write of NetCDF files has repeatedly arisen in the netcdf mailing list (netcdfgroup@unidata.ucar.edu). Read on for a discussion of some options.

This documents outlines a proposal to create an alternate Netcdf-4 file format targeted to high-performance, READ-ONLY, access.