About 10 years ago OODBMS (Poet, Gemstone, Versant, ...) seemed to be starting to replace RDBMS; The idea for using OODBMS was simple - if the programming model is OOP why not persist Objects with an OODBMS directly instead of populating it's properties and class hierarchy into a couple of tables? It was the reason Oracle 8 came with object relational features; But they (OODBMS) failed for following reason:

usually queries using LIKE and leading '%' cannot be indexed. So an idea would be to mirror the string content with the string reverse function to be able to put the '%' operator at the end :

pipelined functions are very comfortable to process incoming data and to return it as structured result set. For this reason they are frequently used in SQL; But be carefully if you join result sets from pipelined function with other tables.

The Oracle optimizer usually uses gathered table statistics to calculate the cardinality of a join operation; For a result set  originated in a pipeline function it has no statistics to evaluate and hence could try to get another path to the data. 

Following SQL retrieves internal employee GUID's from external Id's passed as comma delimited string.

Last week we faced performance problems also shown on the Oracle 10g Db-Console as 'SQL found consuming ...'; The users of the application mourned everything is going slow. Hm ...

The strange thing was that the same kind of SQL run without problems before. I started to monitor I/O with iostat on the Sun  Solaris Database Server. The Storage was based on SAN. The I/O rates were from 5m/s - 10m/s. The devices were about 95%-100% busy and this with an I/O rate with only about 10M/second? Usually 100m/s and more were possible.