I took a look in the sybaseconnection.py module, which I assume is still part of the dev version of sybase. This is the offending function. Regardless of the user's perms it is attempting to modify the value of IDENTITY_INSERT. I'm no sybase guru, but I consulted a DBA who assures me that in Sybase and any TSQL variant (such as Microsoft-TSQL), only "sa" or "dbo" can do "SET IDENTITY_INSERT".
In addition, the fact that this (possibly redundant) statement is excuted before and after and after an SQL transaction goes some way to explain why adding data to Sybase is so slow!
Any suggestions?
def _queryInsertID(self, conn, soInstance, id, names, values):
        table = soInstance.sqlmeta.table
        idName = soInstance.sqlmeta.idName
        c = conn.cursor()
        if id is not None:
            names = [idName] + names
            values = [id] + values
        has_identity = self._hasIdentity(conn, table)
        if has_identity:
            if id is not None:
                c.execute('SET IDENTITY_INSERT %s ON' % table)
                c.execute('SET IDENTITY_INSERT %s OFF' % table)
        q = self._insertSQL(table, names, values)
        if self.debug:
            print 'QueryIns: %s' % q
        if has_identity:
            c.execute('SET IDENTITY_INSERT %s OFF' % table)
        if id is None:
            id = self.insert_id(conn)
        if self.debugOutput:
            self.printDebug(conn, id, 'QueryIns', 'result')
        return id

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