Commented by: @pavel-zotov

It looks like user who was granted to create database can do that only when he first connect to some existent database:

C:\TEMP>isql localhost/3333:e30 -user sysdba -pas masterke
Database: localhost/3333:e30, User: sysdba
SQL> create database 'localhost/3333:c:\temp\e30n.fdb' user 'john' password '123';
Commit current transaction (y/n)?y
Committing.
Statement failed, SQLSTATE = 28000
Your user name and password are not defined. Ask your database administrator to set up a Firebird login.
-Different logins in connect and attach packets - client library error
SQL>
C:\TEMP>isql localhost/3333:e30 -user sysdba -pas masterke
Database: localhost/3333:e30, User: sysdba
SQL> commit; create database 'localhost/3333:c:\temp\e30n.fdb' user 'john' password '123';
Statement failed, SQLSTATE = 28000
Your user name and password are not defined. Ask your database administrator to set up a Firebird login.
-Different logins in connect and attach packets - client library error
SQL>

C:\TEMP>isql localhost/3333:e30 -user john -pas 123
Database: localhost/3333:e30, User: john
SQL> commit; create database 'localhost/3333:c:\temp\e30n.fdb' user 'john' password '123';
SQL> select current_user from rdb$database;

USER

JOHN

Used firebird.conf:

AuthClient = Legacy_Auth,Srp,Win_Sspi
AuthServer = Legacy_Auth,Srp
UserManager = Legacy_UserManager
WireCrypt = Disabled

Commented by: @AlexPeshkoff

Pavel, first of all re
> PS. Why I get "Your user name and password are not defined" if I decided only NOT to *start* 'CREATE DATABASE' statement and wanted to return to SYSDBA session ?
You've decided to not _commit_ last transaction in isql session, i.e. to _rollback_ it. I agree that text is probably far from ideal, but be sure - CREATE DATABASE is executed after answer no:

#⁠ ./isql localhost:employee -user sysdba -pas masterke
Database: localhost:employee, User: sysdba
SQL> create or alter user john password '123';
SQL> revoke all on all from john;
SQL> grant create database to john;
SQL> create database 'localhost:e30n.fdb' user john password '123';
Commit current transaction (y/n)?n
Rolling back work.
SQL> show database;
Database: localhost:e30n.fdb
Owner: JOHN
DB = /tmp/e30n.fdb
Host = localhost
Host = localhost
Host = localhost
PAGE_SIZE 4096
Number of DB pages allocated = 224
Sweep interval = 20000
Forced Writes are ON
Transaction - oldest = 1
Transaction - oldest active = 2
Transaction - oldest snapshot = 2
Transaction - Next = 5
ODS = 12.0
Default Character set: NONE
SQL>

At the same time you can see that error is not reproduced any more. Please recheck yourself with any snapshot after fix for CORE4811 - I had to enhance CREATE DATABASE statement when implementing it and looks like this issue is also gone.

Commented by: @pavel-zotov

> recheck yourself with any snapshot after fix for CORE4811

Checked on WI-T3.0.0.31855 - all works OK, rollback of transaction and new database creation works fine, no such confusing messages.

Commented by: @AlexPeshkoff

Sooner of all has gone when fixing CORE4811