TFileCreateStream = class(TIdFileStream);

TFileCreateStream is a TIdFileStream descendant that implements a file stream which always recreates the file used for storing content written to the stream. 

TFileCreateStream includes a constructor which accepts a file name argument specifying the file on the local file system to create for the stream. 

Use TAppendFileStream to create a file stream which appends stream output to any existing content in the local file. 

Use TReadFileExclusiveStream or TReadFileNonExclusiveStream to create file streams with the desired file sharing modes enabled.