1. An analysis system for analyzing behavior of a database management system (DBMS) being configured to dynamically generates tasks for executing operations when processing a query to a database stored in a storage device having a plurality of storage media to execute the dynamically generated tasks in parallel, the system comprising: a storage resource; and a processor which is coupled to the storage resource, the storage resource being configured to store thread number specifying information which specifies a largest number of threads for the query in the DBMS, first processing number specifying information which specifies a first number of I/O processing that an interface between the DBMS and the storage device can execute in parallel, second processing number specifying information which specifies a second number of I/O processing that can be executed in parallel in the storage medium of the storage device, and third processing number specifying information which specifies a third number of I/O processing that each storage medium can execute in parallel, and the processor being configured to: acquire a number of selected rows corresponding to a key value of an index key for a query from the DBMS; calculate a model-based predicted degree of processing parallelism which is a degree of processing parallelism predicted based on a model of the processing corresponding to the query, based on the number of selected rows, the largest number of threads specified by the thread number specifying information, the first number of I/O processing specified by the first processing number specifying information, the second number of I/O processing specified by the second processing number specifying information, and the third number of I/O processing specified by the third processing number specifying information; acquire, from the storage device, event information on an input-output event with respect to the storage medium when the processing corresponding to the query is actually executed; determine a measured degree of processing parallelism which is a degree of processing parallelism when the processing corresponding to the query is actually executed based on the event information; and perform control of displaying information based on the model-based predicted degree of processing parallelism and the measured degree of processing parallelism.