SE is single threaded
This means each operation is limited to a single hyper-thread within a single CPU core regardless of how many cores your multi-core servers comes with.
Standard edition cannot do parallelism.
SE is licensed by socket rather than core
With SE you can build only a two node cluster,
You have only option of ASM for cluster file system
Oracle Database Standard Edition can only be licensed on servers that have a maximum capacity of 4 sockets.
which means that if you have 1 socket per server you can have a SE RAC cluster with 4 nodes.
Oracle Database 11g Standard Edition is an affordable, full-featured database for servers with up to four sockets. It allows you to save money by buying only what you need today, and then scale out with Oracle Real Application Clusters as demand grows.
Oracle Database 11g Enterprise Edition provides industry-leading performance, scalability, security, and reliability on a choice of clustered or single-servers with a wide range of options to meet user needs.
Basically the truth is:
Using Oracle Database Standard Edition you have “for free” the RAC option, but you will have a limitations of using 4 Sockets. Instead using Enterprise Edition you have to purchase the Option Oracle RAC and no limitation of Sockets.
When licensing Oracle programs with Standard Edition One or Standard Edition in the product name, a processor is counted equivalent to an
occupied socket; however, in the case of multi-chip modules, each chip in the multi-chip module is counted as one occupied socket.
RAC is available with Oracle Enterprise Edition, and under certain conditions, with Standard Edition as well. These restrictions (for Standard Edition) include:
- Must use Oracle Clusterware (no third-party clusterware allowed);
- Must use ASM to store database files; and
- Can only use a max of 4 CPU sockets in the cluster (either 2 nodes with 2 CPUs each, or 4 nodes with 1 CPU each).