Commented by: @pavel-zotov

1. Create new database and run following DDL:

recreate table test(s varchar(1000));
create index test_s on test(s);

2. Create script for ISQL workers (let its name = 'c4236-run.sql'):

set term ^;
execute block as
declare n int = 100000;
begin
while ( n > 0 ) do
begin
execute statement
('insert into test(s) values( ? )')
( rpad('', 1000, uuid_to_char(gen_uuid()) ) )
;
n = n - 1;
end
end
^ set term ;^

3. Run this batch (it will start 10 ISQL sessions):

for /l %%i in (1,1,10) do (
start /min isql /3333:C:\MIX\firebird\QA\fbt-repo\tmp\c4236.fdb -user sysdba -pas masterkey -i c4236-run.sql 1>c4236-run_%%i.log 2>c4236-run_%%i.err
)

4. After 5-10 seconds run:

fbsvcmgr localhost:service_mgr action_properties dbname C:\MIX\firebird\QA\fbt-repo\tmp\c4236-25.fdb prp_shutdown_mode prp_sm_full prp_force_shutdown 0

Messages about it ("335544528 : database C:\MIX\FIREBIRD\QA\FBT-REPO\TMP\C4236-25.FDB shutdown") can be seen only in trace wher both log_errors = true and log_statement_* = true.

But neither 3.0 nor 2.5 will reflect shutdown in c4236-run_*.err files (ERROR logs for each ISQL), i.e. they will remain empty.

Is it correct ?

PS. On 2.5.6 (SC) process of returning from shutdown command is slower than in 3.0 (SS) by dozen times and can last several minutes for 10 attachments.