NOMAD Interface To IMS

The NOMAD IMS Interface is a powerful tool for unlocking the information held in IMS databases.


Companies battling application backlogs with traditional programming languages will find that NOMAD's comprehensive fourth-generation language reduces coding and significantly improves user productivity.

Companies planning to migrate from IMS to DB2 will welcome NOMAD's long-standing relational history and experience in supporting DB2.

For all these companies, the NOMAD IMS Interface delivers the resource control, security and seamless access to multiple data sources needed for their productive use of IMS data.

Using the IMS Interface

Schema Generation

The NOMAD IMS Interface is easy to use. NOMAD's Schema language is used to describe an IMS database. NOMAD provides an automated IMSSCHEM facility that retrieves the necessary information from the IMS libraries and the Interface Control file and generates a skeletal NOMAD Schema.

The user then edits the Schema file, adding additional NOMAD attributes such as headings and display formats, allocates the dataset and compiles the Schema. The user can then access this data with no knowledge of IMS structure.

Access to Multiple File Types

You can define a database that contains descriptions of multiple file types so that your database can, for example, contain NOMAD files, IMS files, DB2 tables and VSAM files. You always have a consistent view of the data, because NOMAD retrieval and analysis commands operate identically on all supported file types, and there are no special sub-environments to access.

Interface Facilities

Centralized Data Definition Control The Schema, NOMAD's internal data dictionary, provides data validation checks, security constraints, null values and display and internal formats.

Automatic Data Synchronization NOMAD protects the integrity of your data by checking the NOMAD definition against the definition of the file you are accessing (IMS, DB2, etc.) and denies access if there is a mismatch. This is an important capability for preventing corruption of databases, or, in the case of a read-only interface, of reporting incorrect information.

Important Security Features Complete control of the data-down to the item level-is provided with NOMAD's powerful security features, which can be combined with any in-house security package. In addition, users such as a Database Administrator (DBA) can create a control file tailored to specific needs. This file can control password access, the number of simultaneous users and the limit on DL/I calls generated without interruption by a specific user.

Audit Facility for Tracking Data Access and Security Violations The IMS Interface automatically tracks all attempted connections (successful or not) and writes them to a NOMAD database where they can be easily queried. Other captured information includes databases accessed, userids and accounts with time stamps, number of DL/I calls, number of positioning commands (FIRST record, NEXT record, LOCATE, etc.) and use of the NOMAD SELECT command, which performs efficient data screening.

Optionally, the IMS DIAGNOSE command causes the interface to track each DL/I command code and Segment Search Argument (SSA) in the audit file. These DIAGNOSE records are time-stamped when passed to IMS and again when data is returned. This is a useful feature in performance tuning.

With this information, the efficiency of IMS access by NOMAD users can be monitored to help achieve better resource control.

Query and Control Commands The NOMAD IMS Interface provides special commands for database allocation, server quiescence, server shutdown and database activity monitoring.

The number of records retrieved for NOMAD and the number of DL/I calls initiated by a single request are also controllable. This ensures a fairer distribution of database access to users requesting simultaneous retrieval. In addition, the DBA can set limits on the number of accesses both DL/I calls and record limits by an individual user, thus avoiding inadvertent attempts to withdraw huge amounts of data.

NOMAD for the Production Environment

The NOMAD IMS Interface has many performance features as well as two modes of operation to facilitate use in a production environment.

Resource Efficiency Facilities

NOMAD has several facilities for improving the efficiency of data retrieval. These include the SELECT command, TEST clause and &INSTANCE_LIMIT variable.

NOMAD SELECT Command. This command enables you to apply selection criteria to the data accessed for all subsequent reports until the SELECT is changed or removed. With this facility, it is not necessary to remember to append an "IF" or a "WHERE" clause to each NOMAD command. NOMAD handles the data screening automatically for all operations.

TEST Clause This clause is useful to test report output without accessing all of the possible records. It retrieves only the designated number of records before returning control to the user.

&INSTANCE_LIMIT This variable controls the number of instances retrieved by any NOMAD retrieval command to prevent runaway requests. It can be set either in the user's access profile or used interactively.

Optional Selection Strategies

The IMS Interface provides the option of using either IMS or the NOMAD IMS Interface to screen data retrieved when screening on non-key fields.
User Exits for Extra Flexibility The NOMAD IMS Interface provides a series of user exits. These programs can be used to communicate with external security packages, to further control access to the IMS database or to have additional data screening performed by IMS.

Multi- or Single-User Mode

The Interface can be used in either single- or multi-user mode, based on installation requirements and user need for data.

Multi-User Mode

In multi-user mode, all users share a single copy of the interface. This mode is implemented using IBM's Cross Memory Services (CMS). Advantages of this mode include maximum security, since the interface resides in the Control Region; fewer BMP (Batch Message Processor) regions; minimal overhead to bring up new users; and minimal impact on the CSA (Common Storage Area). When the NOMAD IMS Interface is run in multi-user mode with the NOMAD MVS Session Manager, further efficiency is achieved from multiple users sharing the same address space outside TSO.

Single-User Mode

In this mode, a copy of the interface resides in each user's region, so CMS is not needed for communication. This method can provide savings of up to 40% in CPU and elapsed time requirements. With this method, the user is also less likely to exceed the limits of the address space when large amounts of data are retrieved.

Use of single-user mode is specified at database access time, so installations can make multi-user mode the default and allow single-region access to selected users.

The Interface Environment

The NOMAD IMS Interface executes as an interactive program providing read-only access to IMS databases. The Interface can be used with IMS databases being updated through IMS/DC, CICS or IMS Batch. The interface runs under ISPF, TSO, MVS Batch or TSO Batch. When run as a batch program under the Batch Message Processor, it provides flexibility for maintaining databases while reporting is performed.

Additionally, in combination with the NOMAD MVS Session Manager, which allows multiple users to share the same address space outside TSO, access from CICS and VTAM is supported.

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