PCIe SSDs are built with SLC NAND flash and designed for applications that require low latency and high IOPs (IO Per Second) operations.  OLTP database workloads which require very low storage IO latency with many small random read/write IO operations are one the idea cases to use PCIe SSDs to ehnance the performance.

To understand how much PCIe SSDs can really improve OLTP database performance, I have conducted  several extensive performance studies on a single node Oracle 11g R2 database as well as a two node 11gR2 Oracle Real Application clusters (RAC) database running on Dell PowerEdge R720 servers with  Dell Express Flash PCIe SSDs on Oracle Enterprise Linux 6.2 platform. 

If you are interested in how much performance gains you can expect these PCIe SSDs and some of the best practices of optimizing Oracle database using PCIe SSDs , you can check out my blog post and a detailed whitepaper published on Dell TechCenter Blogs with the following link: 

http://en.community.dell.com/techcenter/b/techcenter/archive/2012/07/31/optimizing-oltp-oracle-database-performance-using-dell-express-flash-pcie-ssds.aspx