MATLAB: Can’t replace the existing struct in a Mat file

matMATLAB

I am working on a project and have saved many data along the way in a Mat file which is like a database for me. However, starting from yesterday, I have difficulty changing the values of existing struct variables in the Mat file which is currently less than 600MB in size.Detailed structure of the Mat file is at the bottom.
In my codes, I use
mReadable = matfile(datafullfile, 'Writable',true);
so that I don't have to load all of Mat file variables and I have been able to rewrite the variables in the Mat file after making changes by using the following command.
save( datafullfile, 'payoff52', '-append');
However, I can't do that for some variables any longer since yesterday. So I have to save them with a new name to the Mat file. For example, the payoff52 and the IUpayoff both have versions there.
datafullfile is the full path+fileName.
save( datafullfile, 'payoff52', '-append');
Error using save
Can not write file G:\Pm\**\***Data.mat.
Any suggestions? I don't want to keep adding versions of a variable. Thanks!
Name                                       Size                Bytes  Class     Attributes
    B10YrSpd                                  -                  14346  fints               
    B10YrSpd_M              1x1                 28166  struct              
    B10YrSpd_MA              1x1              19628664  struct              
    CopModel                                1x1              57614964  struct              
    IU_Sim                                    1x1             191082104  struct              
    IU_Sim_Scn                                1x1             378620624  struct              
    IUpayoff                                  1x1                 13072  struct              
    IUpayoff01                                1x1                 13072  struct              
    commonDates                              193x1                  1544  double              
    payoff52                                  1x1                534464  struct              
    payoff52_01                               1x1                534464  struct              
    payoff52_02                               1x1                599872  struct              
    sp_HParam                  1x1                 15094  struct              
    sp_HParamSim                    1x1              62402104  struct              
    sp_HParam_PriceMonthly                  -                  17268  fints               
    sPrice_Monthly                            -                  19192  fints               
    spGH_Sim                  1x1              19628664  struct              
    spGHparam                 1x1                 52942  struct              
    spGHparam_FP              1x1                 45106  struct              
    tyM                       -                  51456  fints               
    tyMNS_NA_Param        1x1                232726  struct              
    tyMNS_NA_NA_Sim          1x1              38401280  struct

Best Answer

You should not need to save() a file that you used matfile() with: the writable flag tells it to write the changes itself.
When you do save() a file, there is a chance that you will lose the -v7.3 structure that is needed in order to be able to write with matfile. Without -v7.3 in effect in the .mat, you can at best use matfile() in read-only mode.
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