How to get the latest file from a directory in Server B to Server A?

Shell Programming and Scripting
1 
ssh user@hostnameB
cd /home/oracle
latest_file_target=$(ls -trp -I "*.pd.Sat" -I "*.pd.Lag" -R | grep -v "/.pd" | tail -1)
scp -r $latest_file_target user@hostnameA:$TARGET_DIR/
exit
2

Try (untested)

latest_file_target=$(ssh user@hostnameB 'cd /home/oracle;ls -trp -I "*.pd.Sat" -I "*.pd.Lag" -R | grep -v "/.pd" | tail -1')
scp user@hostnameB:$latest_file_target $TARGET_DIR/