General installation of a one-time installation of DV\PY\PD environment, and then install webserver only need to modify the configuration file once, but if the first installation sequence is as follows:
Dv->webserver->py
At this point, the configuration program is initialized and the Tnsnames.ora file under Jde.ini and webserver must be re-modified
Similarly, if you are doing a PD installation, you still need to install webserver.
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PS: Looks like E910 under the System folder to save all the post-installation environment, it should be possible to first back up the system folder, in the installation of PY/PD environment (if the system has not installed PY/PD environment), Then overwrite the system without having to install webserver again. (not tested, this method is used sparingly)
JDE Develop Server installed DV PY PD after webserver problem