You are trying to import a very large TMX file in an existing SDL GroupShare 2017 server translation memory and you realize that the upload takes a very long time or it even times out.

SDL GroupShare 2017 is able to work with GZIP archives.
Download 7ZIP (http://www.7-zip.org/download.html) and use it to compress the TMX file into a GZIP file. Since it is XML based, the TMX file will be compressed significantly and it's size will be reduced a lot. This should allow you to upload it to the server much faster without any problem.

Steps to proceed after installing and starting 7ZIP:

1. In 7ZIP browse to the folder where your TMX file is located
2. Right-click on the TMX > 7-Zip > Add to archive...
3. Select the Archive format: gzip
4. Click OK.
5. Upload the newly created *.tmx.gz file to the GroupShare server using the server TM import function.

For performance optimization reasons an upload limit can be set on the GroupShare website and therefore very large files cannot be uploaded.
This limit can be changed if needed, but by default it is set to 2GB.