Commented by: @dyemanov

I cannot reproduce this with ISQL on Linux (tried latest v2.5.4 snapshot):

1) start fbserver
2) isql #⁠1: connect localhost:/test/mydb.fdb user 'sysdba' password 'masterkey';
-- success
3) gfix -shut multi -force 0 localhost:/test/mydb.fdb -user sysdba -pass masterkey
-- one second delay, then success
4) isql #⁠2: connect localhost:/test/mydb.fdb user 'sysdba' password 'masterkey';
-- success
5) isql #⁠1: select 1 from rdb$database;
-- error: database shutdown
6) isql #⁠1: quit;
-- success
7) isql #⁠2: quit;
-- success

Commented by: Sean Leyne (seanleyne)

It has been more than a week since the last comment about reproducibility of the issue was posted with no new comments/details provided.

If no new comments/details are posted within the next 3 days, the issue/case will be closed as "Not reproducible".