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5.8.1. Transaction FlowEach of the 4 (non-delivery) transactions is serviced by 2 individual programs, Internet Information System 6.0 (IIS) anda Microsoft COM+ 1.0 Queued Component Server, used as the transaction manager (COM+). Both programs arerunning on the client system:• The initial HTML 1.0 request is serviced by an ISAPI custom-written handler running on Internet InformationSystem 6.0. IIS is responsible for handling all HTML requests. The web server communicates to the COM+ serverthrough a Microsoft COM+ API interface.• COM+ communicates with the server system over Ethernet and handles all database operations, using DB2embedded SQL calls.When the COM+ server boots up, it creates a configurable amount of connections to the server (listed in applicationsettings).COM+ routes the transaction and balances the load according to the options defined in the Component Services GUIfor the COM+ server application and settings in the Windows 2003 registry. The configuration file and registryvariables are listed in Appendix B.2.At the beginning, each TPC-C user sends a pair of HTML 1.0 requests submitting its unique warehouse and districtto the IIS ISAPI handler. Upon successful validation of user's login, IIS the displays an HTML form whichencapsulates the TPC-C transaction menu.The transaction flow is described below:o The TPC-C user requests the transaction type's HTML form and proceeds to generate (fill in) a GET requestwith the required files for the transaction.o IIS accepts the filled in GET request , parses, and validates all values entered by the user.o It then proceeds to transmit those values to the COM+ server through an transaction type specific COM+ apiinterface.o The COM+ Pool Manager receives the request and first decides if there is a connection object in the poolavailable to service it.o If so, the connection is used to send the transaction request to the Server.o If no connection is available, the request will enter a COM+ internal queue and will be serviced by the nextavailable connection.o Once the connection is available to be used, a COM+ pool thread receives the transaction and calls a TPC-C back end DB2 client api to execute all database operations related to the transaction type. (All thetransaction information entered on the HTML form is available in a data structure provided by the ISAPIcaller).o The transaction is committed and the DB2 back end client returns control back to the COM pool thread.o COM pool thread returns control to the ISAPI caller.o (All transaction results are inside the data structure that the ISAPI caller provided to the COM+ api in theparameter list).o ISAPI caller returns control to the "screen application" by doing a PUT request.5.8.2. Database TransactionAll database operations are performed by the TPC-C back-end programs. The process is described below:Using embedded SQL calls, the TPC-C back-end program interacts with DB2 Server to perform SQL datamanipulations such as update, select, delete and insert, as required by the transaction. After all databaseoperations are performed for a transaction, the transaction is committed.DB2 Server proceeds to update the database as follows:When DB2 Server changes a database table with an update, insert, or delete operation, the change is initiallymade in memory, not on disk. When there is not enough space in the memory buffer to read in or write additionaldata pages, DB2 Server will make space by flushing some modified pages to disk. Modified pages are also