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The EntireX z/OS IMS RPC Server allows standard RPC clients to communicate with RPC servers on the operating system z/OS running with IMS in BMP mode. It supports the programming languages COBOL, PL/I and C and can provide IMS-specific PCB pointers for access to IMS databases if needed.

This document covers the following topics:

• Inside the RPC Server

• Impersonation

• Usage of SVM Files

• Automatic Syncpoint Handling

• Scenario I: Calling an Existing COBOL Server

• Scenario II: Writing a New COBOL Server

• Scenario III: Calling an Existing PL/I Server

• Scenario IV: Writing a New PL/I Server

• Scenario V: Writing a New C Server

• Scenario VI: Writing a New Assembler Server

• Returning Application Error Codes from a Server to a Client

Inside the RPC Server

This section covers the following topics:

• IMS-specific PCB Pointers

• Inbuilt Services

IMS-specific PCB Pointers

The IMS RPC Server provides one worker thread. RPC requests are worked off inside the RPC server in the worker thread, which is controlled by a main thread. IMS-specific PCB pointers can be provided as parameters in the linkage section for COBOL and PL/I. They allow you to access the IMS PCB pointer IOPCB, for example to print data or to start an asynchronous transaction and to access IMS databases

IMS-specific PCB pointers are supported with the following programming languages:

• COBOL

  • If the COBOL Wrapper is used, see IMS PSB List.

  • If the IDL Extractor for COBOL is used, see IMS BMP with Standard Linkage Calling Convention.

  For COBOL, the mapping to IMS-specific PCB pointers is done with server mapping files (SVM) files, thus an SVM file is always required. See Usage of SVM Files.

• PL/I

  • If the PL/I Wrapper is used, see PSB List.

  • If the IDL Extractor for PL/I is used, see Preferences.

  For PL/I, the mapping to IMS-specific PCB pointers is done with server interface object(s). They are generated using the PL/I Wrapper (see Scenario III: Calling an Existing PL/I Server) and provided with the parameter stublib to the IMS RPC Server.

Inbuilt Services

IMS RPC Server provides several services for ease-of-use:

• Extractor Service
• Deployment Service
• SMH Listener Service

Extractor Service

The Extractor Service is a prerequisite for remote extractions with the IDL Extractor for COBOL and IDL Extractor for PL/I. See Extractor Service for more information.

Deployment Service

The Deployment Service allows you to deploy server mapping files (SVM files) interactively using the Deployment Wizard (see Server Mapping Deployment). On the RPC server side, the SVM files are stored in a VSAM file as the container. See Deployment Service for configuration information.

SMH Listener Service

With the SMH Listener Service you use the System Management Hub to monitor the RPC server. See Administering the EntireX RPC Servers using System Management Hub under UNIX | Windows.

The SMH Service is switched on if the parameter smhport is set. See parameter smhport under Configuring the RPC Server.

Impersonation

The IMS RPC Server can be configured so that worker threads authenticate the RPC client user ID before execution of the RPC request request with a mainframe security repository (RACF, CA Top Secret or CA ACF2), using the SAF interface. If the RPC user ID is valid, the worker thread gets the identity of the RPC client. This is necessary when accessing (security) protected data sets. The way authentication is carried out can be controlled by the RPC parameter impersonation.

• For impersonation value AUTO, the IMS RPC Server does not validate RPC passwords, so you have to make sure the RPC client is correctly authenticated, either by using a secure EntireX Broker (validation must be against the correct mainframe security repository where z/OS user IDs are defined) or with your own security implementation.

• For impersonation value YES, the IMS RPC Server uses the RPC user ID and password supplied by the RPC client for authentication and impersonation of the client. This means that the RPC server validates the password.

The picture above shows the configuration impersonation=yes.

The lifetime of an impersonated task starts when an open request for an RPC conversation or a non-conversational RPC request is received. It ends when the RPC conversation stops (after a commit operation or timeout) or when the non-conversational RPC request has been performed.

Usage of SVM Files

To correctly support special COBOL syntax such as JUSTIFIED, SYNCHRONIZE and OCCURS DEPENDING ON clauses, LEVEL-88 fields, etc., the IMS RPC Server requires in many situations a server mapping file.

SVM files contain COBOL-specific mapping information that is not included in the IDL file and therefore not sent by an EntireX RPC client to the RPC server. See also When is an SVM File Required? under Handling SVM Files.

The RPC server marshalls the data in a two-step process: the RPC request coming from the RPC client (Step 1) is completed with COBOL-specific mapping information taken from the SVM file (Step 2). In this way the COBOL server can be called as expected.

The SVM files are retrieved as a result of the IDL Extractor for COBOL extraction process and the COBOL Wrapper if a COBOL server is generated.

You can customize the usage of the SVM file using parameter svm. See Configuring the RPC Server.

Note:
SVM files are used for COBOL only.

Automatic Syncpoint Handling

The IMS RPC Server issues a SYNC | ROLB call under the following circumstances:

• After a successful non-conversational request or an end-of-conversation, the server issues an IMS SYNC call.

• After abnormal termination of a non-conversational request or a conversation due to an error, the server performs an IMS ROLB call to back out any pending database modifications.

Scenario I: Calling an Existing COBOL Server

To call an existing COBOL server

1. Use the IDL Extractor for COBOL to extract the Software AG IDL and, depending on the complexity of the extraction, also an SVM file. If your COBOL server uses PCB pointers, see IMS-specific PCB Pointers.

2. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

See Client and Server Examples for z/OS IMS BMP for COBOL RPC Server examples.

Scenario II: Writing a New COBOL Server

To write a new COBOL server

1. Use the COBOL Wrapper to generate a COBOL server skeleton and, depending on the complexity of the extraction, also an SVM file. Write your COBOL server and proceed as described under Using the COBOL Wrapper for the Server Side. If your COBOL server uses PCB pointers, see IMS-specific PCB Pointers.

2. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

See Client and Server Examples for z/OS IMS BMP for COBOL RPC Server examples.

Scenario III: Calling an Existing PL/I Server

To call an existing PL/I server

1. Use the IDL Extractor for PL/I to extract the Software AG IDL.

2. If your PL/I server uses PCB pointers, generate one or more server interface objects, using the Software AG IDL File extracted in Step 1 above. For more information see Extraction Result in the IDL Extractor for PL/I documentation. See also IMS-specific PCB Pointers.

3. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

See Client and Server Examples for z/OS IMS BMP for PL/I RPC Server examples.

Scenario IV: Writing a New PL/I Server

To write a new PL/I server

1. Use the PL/I Wrapper to generate a PL/I server skeleton. Write your PL/I server and proceed as described under Using the PL/I Wrapper for the Server Side. If your PL/I server uses PCB pointers, see IMS-specific PCB Pointers.

2. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

See Client and Server Examples for z/OS IMS BMP for PL/I RPC Server examples.

Scenario V: Writing a New C Server

To write a new C server

1. Use the C Wrapper to generate a C server skeleton and a C server interface object. Write your C server and proceed as described under Using the C Wrapper for the Server Side (z/OS, UNIX, Windows, BS2000/OSD, IBM i).

2. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

Scenario VI: Writing a New Assembler Server

To write a new Assembler (IBM 370) server

1. Build an RPC server in Assembler. Here are some hints:

   • The RPC server is dynamically callable (no pre-initialization required).

   • The parameter interface is either compatible with the COBOL or PL/I calling convention (IDL level parameter will be passed in the address list).

   • The alignment of integer or float data types is considered. The HASM Assembler aligns integer or float data types to appropiate boundaries. For example:

     ...
           MyLabel   DSECT
           MyField1  DS   H                      I2
           MyField2  DS   F                      I4
           MyField3  DS   E                      F4
           MyField4  DS   L                      F8

   • The IMS RPC Server will not align these data types by default.

   • To force alignment by definition in your IDL file (see the aligned attribute within the attribute-list) before generating your RPC client. For information on whether your client supports the aligned attribute, see Mapping the aligned Attribute to C | COBOL | DCOM | .NET | Java | Natural | PL/I.

2. Build an EntireX RPC client using any EntireX wrapper. See EntireX Wrappers. For a quick test you can:

   • use the IDL Tester; see EntireX IDL Tester in the EntireX Workbench documentation

   • generate an XML mapping file (XMM) and use the XML Tester for verification; see EntireX XML Tester

Returning Application Error Codes from a Server to a Client

See Returning Application Errors from a Server under z/OS IMS to a Client in the COBOL Wrapper documentation under Writing Applications with the COBOL Wrapper.

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