Going from text to clob is not something we do.

Also Oracle DB has problems with this, see
http://abhijitbashetti.blogspot.de/2011/10/converting-varchar2-to-clob-and-clob-to.html

tests/data/db_structure2.xml

@@ -49,8 +49,9 @@
 
    <field>
     <name>description</name>
-    <type>clob</type>
+    <type>text</type>
     <notnull>false</notnull>
+    <length>1024</length>
    </field>
 
    <field>

tests/lib/dbschema.php

@@ -53,12 +53,6 @@ class Test_DBSchema extends PHPUnit_Framework_TestCase {
 	}
 
 	public function doTestSchemaChanging() {
-		if (OC_Config::getValue( 'dbtype', 'sqlite' ) === 'oci') {
-			$this->markTestSkipped(
-				// see http://abhijitbashetti.blogspot.de/2011/10/converting-varchar2-to-clob-and-clob-to.html
-				'Oracle does not simply ALTER a VARCHAR into a CLOB.'
-			);
-		}
 		OC_DB::updateDbFromStructure($this->schema_file2);
 		$this->assertTableExist($this->table2);
 	}