The topic of a String
can get a bit specific to your use case. I'm assuming you're using Eureka, but do mention if it's another.
From http://wiki.servicenow.com/index.php?title=Introduction_to_Fields#Increasing_the_Length
For 254 characters or less, the string field will be a single-line
text field. Anything 255 characters or over will appear as a
multi-line text box.
Then the String
limits are based on what database your instance is running on. Oracle is limited to 4000 characters, but you can put in a request to ServiceNow for a specific field to be increased in size. In case of that, they will need to change the datatype themselves for that.
For an instance running on MySQL, you have more flexibility on your own.
Take a look at the reference between ServiceNow field types and MySQL. http://wiki.servicenow.com/index.php?title=Introduction_to_Fields#Database_Field_Types
In particular the String
types
Field Type Options Dictionary MySQL DB Type
String small string VARCHAR(40)
String medium string VARCHAR(100)
String large string MEDIUMTEXT
String extralarge string MEDIUMTEXT
If you choose a type of large or extralarge your field will use the MySQL field of MEDIUMTEXT
which has the following limits based on this question Maximum length for MySQL type text
MEDIUMTEXT - 16,777,215 bytes
This now gets in to the type of data you're inputting into the field. I believe ServiceNow uses UTF8 for characters, so if you are generally limited to single byte characters you can store that many characters.
If you are using multi-byte characters, you will have less available but still quite a few.
Be careful when using a lot of characters since it may impact performance. Consider using a Journal field if applicable.