-24991: ERR_ NOSQLUSERSESSION - no sql user session available 

Explanation:

A session with a database-kernel user task is required for the DBM server command you have chosen.

User action:

Start the session with the DBM server command sql_connect or with the Database Manager option –uSQL (CLI).

Check whether a previous attempt to set up the session failed and read the error message issued for it.

If the error occurs in the Database Manager GUI and there is no way in which you can correct it, please contact your local support organization.