The number of subpools on your system can be easily determined by either looking at the instance parameter _kghdsidx_count or by counting the number of rows in x$kghlu.

Figure 7-13 shows a series of SQL statements related to shared pool subpools. In this case, a 752MB shared pool exists with three subpools. The x$ksmss query returns one row for each subpool plus another row if the Java pool exists. The instance parameter to set the number of subpools, _kghdsidx_count cannot be altered dynamically. If you want to influence Oracle to invoke a subpool number change, you must set the instance parameter and recycle the instance.

Oracle does place a hard limit on the number of subpools. In Oracle Database 11g, I was able to start an instance with seven subpools, but with eight subpools, the instance did not start-in fact, it required a shutdown abort before it could be restarted.