If you mean the messages such as the following:
Warning: Vlan 111 name length exceeded the recommended length of 20 characters.
then is just an informational message. You are allowed to assign vlan names up to 32 characters.
In IOS, the VLAN name length has always had a maximum length of 32 characters and if the name is greater than 32 characters, then it is truncated. This behavior is the same for all switches running IOS.
It is all to do with VTPv3 - basically if you were to configure all 4000 VLAN names with 32 characters, there wouldn't be enough space in NVRAM to store the VLAN configs. So the recommended limit i VTPv3 is in use (or planned to be in future) is to limit the names to 20 characters. If you aren't using VTP (or if it's unlikely you'll be configuring all 4K VLANs!), you can safely ignore this warning.
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If you upgrade a switch that WAS running VTP 2.0, I could put in all 32 characters. However, i find that after upgrading to vtp3, I can NOT enter anything longer than 20 characters. Is there a way to over-ride this?
Defines a text string used as the name of the VLAN; valid values are from 1 to 32 characters.
thats just informational message