In order to modify a field size for a geo spatial attribute field. Please follow the below instructions.
- Open ArcCatalog, expand your file geo database and find the feature class you want to edit the field.
- Right click on the Feature Class and select properties.
- You will see the properties window (see screenshot below).
- Select the field that needs to be modified
- In the field properties, change the length of the field.
How to modify field size for an attribute in SDE db using ArcCatalog