Thank you for your answer.
But, I have a problem.
"Resume last session" always gives me a information.
For example :
Continue the interrupted session (2006-09-01 12:34:48, URLs added: 396, estimated URLs left: 2041)
However, the file sitemap.xml is built and all the links are present in the file.
If the file sitemap is built, "Resume last session" does not have to give a information ?
I does not understand "estimated URLs left: xxxx".
Also, sometimes I build the file again.
Consequently, if I obtain the date of Ping, I would have the possibility of checking if it were already sent.
I would thus avoid sending several Ping to Google...
Thank you for your assistance.