I found how to get sizes, with the control center, but something is strange :
There is 2 tablespaces : <MyTableSpace> and userspace1 (I know this is not good)
From the first one, I can get all the sizes, but on the second, all the sizes and numbers of rows are null, even tables are not empty (some are countaining thousands of lines).
How can I do to get all the missing datas ? (without changes anything, if it's possible)
No, the command is not just RUNSTATS. Look in the "Command Reference for how to run it. There are various options that you can use. It depends on your particular situation. You can use the Control Center to do RUNSTATS. Just highlight the tables you want done (you can do more than one at a time), right click, choose runstats, and select the options you want from the wizard.