The following procedure solved my problem. It allowed the repository to work integrated with Redmine (user mapping) and authenticated for SVN repository.
(Assuming you have Subversion's libapache2-svn packages and have restarted apache2 service)
create SVN parent directory
<pre>
mkdir /svn
</pre>
Open /etc/apache2/mods-enabled/dav_svn.conf with an editor
<pre>
<Location /svn>
DAV svn
SVNParentPath /svn
AuthType basic
AuthName "SVN repositories"
AuthUserFile /svn/auth
Require valid-user
</Location>
</pre>
create htpasswd file and add a user, for adding just remove -c argument
<pre>
htpasswd -cm auth /svn/auth admin
</pre>
setup permissions
<pre>
chown -R www-data:www-data /svn
chmod -R g+ws /svn
</pre>
restart Apache
<pre>
service apache2 restart
</pre>
some changes also are needed in Redmine
<ul>
<li>Setup crontab for managing repositories with redmine</li>
<li>when you browse the repository from redmine and you get a 404 error then go to project settings-> repositories-> your repository [edit]
<ul>
<li>Username = admin</li>
<li>Password is admin's password</li>
</ul>
</li>
</ul>
you can browse/checkout/commit/etc from h..p://host/svn or via Redmine for browsing and use other tools like TortoiseSVN for checkout/commit/edit/etc..