Unable to reverse engineer a database

[viardot]

Windows 10 version 2004 build 19041.603
ERDesinging 3.1.0.0
HSQLDB 2.5.1

With ERD connect to a HSQLDB

• Dialect : HSQLDBDIALECT
• Alias : Study
• Driver : org.hsqldb.jdbc.JDBCDriver
• JDBC-URL: jdbc:hsqldb:file:C:\hsqldb-2.5.1\hsqldb\data\study
• user : sa

Result of pressing test button is: "The connection seems to be ok DB : HSQLDB database engine 2.5.1"

Pressing Database | Reverse engineer...
Error: Database lock acquisition failure: lockFile: org.hsqldb.persist.LockFile@33da0460[file = C:\hsqldb-2.5.1hsqldbdatastudy.lck, exists=true, locked=false, valid=false,] method: checkHeartbeat read: 2020-11-18 12:07:45 heartbeat - read: -1610ms.

The data base can be opened and edited by HSQLDB Manager.

Additional the schema of this db is:

drop table if exists College;
drop table if exists Apply;
drop table if exists Student;

create table College(cName longvarchar, state longvarchar, enrollment int);
create table Student(sID int primary key, sName longvarchar, GPA real check(GPA <= 4.0 and GPA > 0.0 and GPA is not null), sizeHS int);
create table Apply(sID int, cName longvarchar, major longvarchar, decision varchar(1), foreign key (sID) references Student(sID));

[mirkosertic]

Your database seems to be locked by another process. Please make sure no other process has access to the database and no lockfile is in the database directory.

[viardot]

True the data base is locked by ERD self.
Is there a way to disconnect the database from ERD?