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This is part thirteen of the series that began with
What is System-Managed Storage?
What is Distributed FileManager?
Today's complex data processing environment often requires accessing data that is distributed among many different computer systems. Distributed FileManager/MVS (DFM/MVS) helps solve the problems of distributed data processing. It offers services for accessing and processing MVS/ESA data from remote computer systems as if the data were local to the remote systems.
DFM/MVS was initially offered in DFSMS/MVS Version 1 Release 2. It is a Distributed Data Management Architecture (DDM) server implementation on MVS/ESA systems which uses DDM commands as its language for remote data access. DDM provides a vocabulary and set of rules for sharing and accessing data among like and unlike computer platforms. It includes a set of standardized file models and access methods that allows users and applications to access remote data without needing to upload and download files.
DFM/MVS provides DDM client implementations on heterogeneous systems with remote access to MVS/ESA data. Applications can access the data independent of where it is located. Using the DFM/MVS server can significantly improve your ability to access MVS/ESA data from applications running on client systems. DFM/MVS works with DDM client implementations on OS/2, AIX, and OS/400 systems.
Extended Enterprise Data Access
An extended enterprise environment often includes both centralized hosts and distributed workstations. Most applications in an extended enterprise share data to some degree. Therefore, data in an extended enterprise must be in a form that can be shared throughout an enterprise. Multiple workstations must have access to the same data with the MVS/ESA system providing data sharing and serializing at the data set level.
Data access (the ability to create, read, and write data) should be transparent to applications regardless of the internal format and location of the data. In addition, applications must at all times access latest copy of the data.
Avoiding unnecessary data duplication is also desirable. Uncontrolled duplication leads to storage management problems and wasting of storage resources. In contrast, controlled duplication for backup and migration is useful and necessary. Wherever applications run in your enterprise, they should be able to access data without unnecessary uploading and downloading. You should be able to store data on your MVS/ESA systems while accessing and sharing it across the enterprise. DFM/MVS provides your applications with the ability to do so.
A key objective of DFSMS/MVS is to offer products that provide workstations with both record- and stream-oriented data access to MVS/ESA data. DFM/MVS enables remote clients in your network to create, read, and write data on MVS/ESA systems with the following requirements:
- You can create and access both SMS-managed and non-SMS-managed data sets.
- All data sets accessed must be cataloged in an ICF catalog.
- All data sets accessed must reside on direct access storage.
- All data sets accessed must be supported by DFM/MVS.
DFM/MVS supports remote access to the following MVS/ESA data set types:
- BSAM and QSAM data sets
- VSAM ESDSs, KSDSs, RRDSs, VRRDSs, and alternate indexes for an ESDS or KSDS
- PDSs and PDSEs
DFM/MVS does not support remote access to:
- VSAM linear data sets
- Generation data groups and generation data sets
- BDAM data sets
- ISAM data sets
- Sequential data striping data sets
- OpenEdition MVS HFS files
ACS Routines for DFM/MVS
Normally, DFM/MVS permits remote creation of MVS/ESA data sets which are SMS-managed, although you can set up your DFM00 member of SYS1.PARMLIB to allow creation of non-SMS-managed data sets. For data sets to be SMS-managed, they must be assigned a storage class. ACS routines are used to determine the SMS classes for data sets.
The fragment of a storage class ACS routine below might be used to ensure that a storage class is assigned to the new data set.
IF &JOB = 'GDEDFM' AND &STORCLAS = '' THEN
DO
SET &STORCLAS = 'DFMCLASS'
EXIT CODE(0)
END /* DO */
Similarly, you can use the &JOB ACS read-only variable to assign an appropriate data class and management class in the data class and management class ACS routines respectively.
DFM/MVS Security
RACF, or an equivalent product, is used to control which source systems are authorized to initiate conversations with DFM/MVS. By setting up RACF resource class profiles, you can define which user IDs or groups are authorized to access DFM/MVS services. You can use RACF resource class profiles to define administrators with update authority to authorize access to DFM/MVS. Once a conversation is initiated, DFM/MVS uses RACF services to control the actual data access as well.
DFM/MVS Scenarios
DFM/MVS offers distributed data processing solutions for a broad range of diverse applications. Here are just a few of the many possibilities:
- Insurance industry
- PC applications can present insurance data to underwriters. OS/2 source systems can connect with DFM/MVS on a target MVS/ESA system and remotely access and update insurance information.
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Chemical industry
- An OS/400 can transmit orders to DFM/MVS providing access to MVS/ESA data sets for centralized tracking. An OS/400 might contain personnel data for security guards at one establishment. Daily personnel updates can be retrieved from an MVS/ESA system using DFM/MVS.
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Banking and finance industries
- Foreign currency transactions on a branch OS/400 can be transmitted to a central MVS/ESA system using DFM/MVS.
In Summary
DFM/MVS allows clients to share and access data on MVS/ESA servers regardless of where the data is located.
- It allows remote clients to access MVS/ESA data at the record and stream level, so they need not download and upload entire files.
- It provides access to SAM, VSAM, PDS, and PDSE data on MVS/ESA.
- It allows remote clients to create, delete, read, and write MVS/ESA data.
- It provides applications and end-users with transparent access to MVS/ESA data using local commands
- It improves the productivity of application programmers by eliminating upload and download time and allowing data to be shared in place.
- It capitalizes on strengths of centralized data storage and provides MVS/ESA storage and data management techniques for workstation data
- It leverages existing investments in data, applications, support skills, and storage capacity.
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