Distributed and local connectivity with the IMS Universal drivers

The IMS Universal drivers support distributed (type-4) and local (type-2) connectivity to IMS databases.

Distributed connectivity with the type-4 IMS Universal drivers

With type-4 connectivity, the IMS Universal drivers can run on any platform that supports TCP/IP and a Java™ Virtual Machine (JVM), including z/OS®. To access IMS databases, the type-4 IMS Universal drivers first establish a TCP/IP-based socket connection to IMS Connect. IMS Connect is responsible for routing the request to the IMS databases by using the Open Database Manager (ODBM), and sending the response back to the client application. The DRDA protocol is used internally in the implementation of the type-4 IMS Universal drivers. You do not need to know DRDA to use the type-4 IMS Universal drivers.

The type-4 IMS Universal drivers support two-phase commit (XA) transactions. IMS Connect builds the necessary z/OS Resource Recovery Services (RRS) structure to support the two-phase commit protocol. If two-phase commit transactions are not used, RRS is not required.

To establish a connection to IMS, the driverType connection property must be set to indicate distributed (type-4) connectivity to IMS

After successful authentication, the IMS Universal drivers send other socket connection information, such as program specification block (PSB) name and IMS database subsystem, to IMS Connect and ODBM to allocate the PSB to connect to the database.

A connection to an IMS database is established only when a program specification block (PSB) is allocated. Authorization for a particular PSB is done by the ODBM component during the allocation of a PSB.

The type-4 IMS Universal drivers support connection pooling, which limits the time that is needed for allocation and deallocation of TCP/IP socket connections. To maximize connection reuse, only the socket attributes of a connection are pooled. These attributes include the IP address and port number that the host IMS Connect is listening on. As a result, the physical socket connection can be reused and additional attributes can be sent on this socket to connect to an IMS database. When a client application of the type-4 IMS Universal drivers makes a connection to IMS, this means:

A one-to-one relationship is established between a client socket and an allocated PSB that contains one or more IMS databases.
A one-to-many relationship is established between IMS Connect and the possible number of database connections it can handle at one time.
IMS Connect does the user authentication.
ODBM ensures that the authenticated user is authorized to access the given PSB.

The following figure shows how the type-4 IMS Universal drivers route communications between your Java client applications that are running in a distributed environment and an IMS subsystem.

The boxes on the far left represent different types of Java applications that run in a distributed environment, including Java EE applications, stand-alone JDBC applications, and stand-alone DL/I applications in Java. Java EE applications can run only from within a WebSphere Application Server container. The box in the center represents a new IMS component, called the type-4 IMS Universal drivers, which provide network connectivity to the IMS database from a distributed environment. The network connection is made by using the DRDA protocol, which is sent through TCP/IP. The rectangle on the right represents the IMS Connect component, which sits as the connection gateway to the z/OS environment. IMS Connect receives requests from the IMS Universal drivers and routes them to Open Database Manager component and to the IMS database.

You can also use the type-4 IMS Universal drivers if your Java clients are running in a z/OS environment but are on a separate logical partition from the IMS subsystem. Use type-4 connectivity from a z/OS environment if you want to isolate the application runtime environment from the IMS subsystem environment.

Local connectivity with the type-2 IMS Universal drivers

Local connectivity with the type-2 IMS Universal drivers is targeted for the z/OS platform and runtime environments. Use type-2 connectivity to connect to IMS subsystems in the same logical partition (LPAR).

The following table shows the z/OS runtime environments that support client applications of the type-2 IMS Universal drivers.

Table 1. z/OS runtime environment support for the type-2 IMS Universal drivers
z/OS runtime environment	Type-2 IMS Universal drivers supported
WebSphere® Application Server for z/OS or WebSphere Application Server Liberty	IMS Universal Database resource adapter
IMS Java dependent regions (BMP, JMP, JBP, IFP, and MPR regions); CICS	IMS Universal DL/I driver IMS Universal JDBC driver
CICS OSGi JVM server	IMS Universal DL/I driver IMS Universal JDBC driver
CICS Liberty JVM server	Not supported
Db2 Java Stored Procedures	Not supported
z/OS batch	Not supported

Because it runs on the same LPAR as the IMS subsystem, during connection time, a client application of the type-2 IMS Universal drivers does not need to supply an IP address, port number, user ID, or password. The driverType property must be set to indicate local (type-2) connectivity to IMS.

The following figure shows how the type-2 IMS Universal drivers route communications between your Java client applications that are running in an LPAR inside a z/OS mainframe environment and an IMS subsystem that is located in the same LPAR.

The boxes on the far left represent Java application programs that are running in a logical partition inside a z/OS mainframe environment. These Java applications can run in WebSphere Application Server for z/OS, IMS Java dependent regions, Db2 for z/OS stored procedures, or CICS. The box in the center represents the IMS Universal drivers, which provide type-2 network connectivity to an IMS database in that logical partition. The type-2 IMS Universal drivers routes the application request directly to IMS, or through the Open Database Access (ODBA) and the Database resource adapter (DRA) components.

RRSLocalOption connectivity type

In addition to type-4 and type-2 connectivity, the RRSLocalOption connectivity type is supported by the IMS Universal Database resource adapter running on WebSphere Application Server for z/OS. With RRSLocalOption connectivity, applications using the IMS Universal Database resource adapter do not issue commit or rollback calls. Instead, transaction processing is managed by WebSphere Application Server for z/OS. Two-phase commit (XA) transaction processing is not supported with RRSLocalOption connectivity type.