JDBC mediator performance considerations and limitations

JDBC mediator performance considerations and limitations

Known database limitations

Sybase before V12.5.1 does not support in-line queries in the “from” clause, and therefore does not support multiple table DataGraphs with filters. To use the Service Data Object in WAS use Sybase V12.5.1.
The Informix Dynamic Server does not support sub-selects, which are needed for multiple table graphs. Use Informix Extended Parallel Server.
Oracle 8i does not support the ANSI join syntax. The mediator in multiple table cases requires Oracle 9i or 10g.

Performance recommendations

Evaluate if your target projects are well suited to these technologies. In general, projects that are read-intensive and require disconnected data are good candidates.
Limit the number of tables in the metadata. One or two is best because relationships, with respect to filters, become ambiguous when graphs have many branches.
Work with small data sets as often as possible to avoid consuming excessive amounts of memory within your applications. We can limit the amount of data returned to the SDO by specifying filters in the metadata objects or by using paging.
For Web applications, if the DataGraph is not too large and is to be reused later, store it in the user session.