I had not tried selecting more than one file when importing and this makes things easier. Thanks.
I have read the section about optimizing for large amounts of data and followed the suggestions there. However, this does not change the fact that memory is used for each imported file and at some point the memory is all used up. I can imagine that the swap memory is then used which really slows things down. Saving the DB does not reduce the memory used, only closing the program. I have attached pictures of the system stats before and after importing three files. You can see how the available memory drops from 1.15GB to 0.32GB after the import. In the first picture you can see how the swap file is reduced in size after the program has been exited. The save before exiting did not redurce the file.
The section on optimization also suggests only importing the data set which I need. Good idea. All 91 files have the same format, but with 98 channels, I do not want to search out the 51 channels I need 91 times. Do you have something like a template function where I can select the 51 channels I need 1 time, save the template and then use it to import the other 90 files?