ADIOS I/O type Limitations/On-going work

-- DRAFT --
**ADIOS I/O TYPE LIMITATIONS**
**SCORPIO**
* Reading/writing with different I/O decompositions does not work
* Reading/writing with different number of MPI processes does not work
* Open to update a variable does not work
* Open to append an existing file does not work
* Overwriting existing attributes (with multiple pio_put_att calls on the same attribute) does not work
* Get of variables with dimensions >= 4D is not supported
* Redefine mode (to rename or delete an existing variable or attribute) is not supported
* To put/get a NetCDF variable (the variable type does not matter), the write buffer for pio_get_var and the read buffer for pio_get_var must use the same data type. If we use a double type write buffer to put a NC_INT variable and later use a float type read buffer to get it, the read buffer would contain incorrect values (missing required double to float type conversion)

**ESMCI CIME**
* CIME checks for NetCDF files for restart runs (requires files in the "*.nc" extension). ADIOS "files" have "*.bp" extension.
** As a workaround one can create dummy "*.nc" files corresponding to "*.bp" files to circumvent the CIME check
UPDATE: For ADIOS file (BP directory) foo.nc.bp SCORPIO now creates a corresponding symbolic link foo.nc

**E3SM**
* MPAS does not support read using the ADIOS I/O type (the changes in env_run.xml XML file is not reflected in MPAS stream files)

**SUGGESTED ENHANCEMENTS**
**E3SM**
* Allow E3SM/SCREAM to write restart files and history files using different I/O types (e.g. Write restarts using ADIOS while writing history files using PnetCDF)