SQL Server – Do You Need to Detach a Database to Attach It?

This one was quite tricky. I didn't figure out how to access DBCC messages, but am working on it. Anyway, this Powershell script attaches databases, executes DBCC CHECKDB and detaches dbs.

# Get database files from where ever they are
$databases = gci "C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data2\*.mdf"
$sqlCmds = @()
# Parse db names from file names somehow and generate attach/check/detach statements
foreach($db in $databases) {
  $dbName = [regex]::Replace($db.Name, "(?i)\.mdf", "")
  $lgName = [regex]::Replace($db.FullName, "(?i)\.mdf", ".ldf")
  $sqlCmds += $("CREATE DATABASE {0} ON (FILENAME = '{1}') LOG ON (FILENAME = '{2}') FOR ATTACH;"  -f $dbName, $db.FullName, $lgName)
  $sqlCmds += $("DBCC CHECKDB ({0});" -f $dbName)
  $sqlCmds += $("EXEC sp_detach_db @dbname='{0}';" -f $dbName)
}

[void][Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.ConnectionInfo")
$conn = new-object Microsoft.SqlServer.Management.Common.ServerConnection
$conn.ConnectionString = "Server=SERVER\INSTANCE;Database=master;Integrated Security=True"
$s = $sqlCmds[0]

# Try and execute the statements   
try {
    foreach($s in $sqlCmds) {
      $ret = $conn.ExecuteNonQuery($s)
      $ret
    }
} catch [system.exception] {
  $_.Exception.ToString()
}

This isn't an access issue. The problem is that you are attaching the database to a higher version of SQL Server than the instance the .mdf was originally attached to and it's read only. SQL Server is trying to upgrade the database as part of the attach and can not because the db is in read-only mode.

If your database is in READ_ONLY (which sounds like it is the case based on your error messages), then you need all files (both log and data) to attach it per the Technet documentation. If you look under the FOR ATTACH clause, it explicitly describes that:

...for a read-only database, the log cannot be rebuilt because the primary file cannot be updated. Therefore, when you attach a read-only database whose log is unavailable, you must provide the log files or files in the FOR ATTACH clause.

You need the accompanying .ldf for the database. I would contact whoever provided the database and ask them to provide both the .mdf and .ldf files. Then, you can attach it with the following syntax:

CREATE DATABASE [foo]
ON (FILENAME='<<path to mdf>>')
LOG ON (FILENAME='<<path to ldf>>')
FOR ATTACH;

The READ_ONLY status cannot be removed from the database without attaching it because it is stored in the metadata of the database. To alter it, the database needs to be online and attached.

Another alternative is to ask for a backup of the database. You can work around some of these issues more easily if you're doing a database restore instead of an attach.