MS Access DB Error while using ALTER TABLE

[eluser]Unknown[/eluser]
Hello community,

i am new to codeigniter and i am developing a kind of cms core functions. I need some functions using e.g. the "ALTER TABLE"-SQL-Statement. But using this i am getting an error:

Code:

ERROR - 2014-08-17 21:44:18 --> Severity: Warning  --> odbc_exec(): SQL error: [Microsoft][ODBC Microsoft Access Driver] Das Datenbankmodul konnte die Tabelle 'tbl_adminPermission' nicht sperren, da sie bereits von einem anderen Benutzer oder Vorgang bearbeitet wird., SQL state S1000 in SQLExecDirect "PATH"\system\database\drivers\odbc\odbc_driver.php 153

Translattion: The database modul could not block the table tbl_adminPermission, because it is used by another user or action, SQL state s1000 SQLExecDienst.

I am using a system DNS to connect to the database and the odbc driver.

Is there anybody who has some experience with this kind of error?

Thanks in advance.

Christoph