00C900C8

Explanation
 Access to the index is disallowed within the same
commit scope as an ALTER TABLE statement that alters the key column
in the index. If the ALTER TABLE statement failed, then commit the
changes to the index and retry the ALTER TABLE statement. If an INSERT,
DELETE, UPDATE, MERGE or SELECT statement failed, then commit the
ALTER and retry the statement.

System action
  The operation is not allowed.

User response
  Commit and then retry the operation.