Without quotes, toronto will be treated as TORONTO (upper case) by Oracle.
But looks like PDB created with name in lower case explicitly. So we have to enclose the pdb name in quotes in order to refer it in correct case.
Got it!. Many thanks
As stated, whomever/whatever created that PDB must have done something like:
CREATE PLUGGABLE DATABASE "toronto" ...
Because the PDB name was in double quotes, the case sensitivity was carried forward and the PDB was created with a lower case name as your SHOW PDBS command has illustrated. So you'll need to always wrap the PDB name in double quotes when you are working with it. I would get terribly frustrated if this were my situation. I'd look to fix it. But that is totally up to you.
If you desire to fix this, simply unplug the PDB and plug it back in with the proper name. Instructions can be found here: https://oracle-base.com/articles/12c/multitenant-pdb-archive-files-for-unplug-and-plugin-12cr2
You will just be unplugging from the CDB and plugging back into the same CDB. This will obviously require downtime.