The three-tier, gateway-enabled environment uses a DirectConnect for z/OS Option gateway for communication between LAN applications and the mainframe.
Figure 2-1 illustrates the use of the Mainframe Connect options in a three-tier, gateway-enabled environment.
Figure 2-1: Gateway environment (with DirectConnect for z/OS Option)
As shown in Figure 2-1, the Sybase or user-written client on the LAN (Windows or UNIX) sends a request for data from the mainframe to the DirectConnect for z/OS Option in the gateway. The DirectConnect for z/OS Option then sends the request to one of the DB2 UDB Options or a Server Option application on the mainframe. The DB2 UDB Option accesses DB2 UDB for z/OS and the Server Option application accesses other mainframe data and both return the data or a message to the LAN client through the gateway.
The LAN client can be:
User-written – user-written clients can be any application using ODBC or JDBC and created with or without Sybase tools, such as PowerBuilder®, Open Client, or Open Server.
Sybase servers acting as clients – these include EAServer, ASE/CIS, and Replication Server.
The DirectConnect for z/OS Option gateway can be a TRS using RPCs or a DB2 access service using SQL in communication from the LAN to the mainframe. TRS can be used for RPCs and language requests.
The Server Option and the DB2 UDB Option both reside on the mainframe.
The accessed database can be a relational source, such as DB2 UDB. Access to non-relational data (not shown in Figure 2-1), such as IMS, VSAM, IDMS, DATACOM, and ADABAS, requires some user application development.
