8.1.2 MVS System Requirements

IMS/ESA requires a Type 2 SVC in the MVS nucleus and a Type 4 SVC in

LPALIB.

IMS/ESA Resource Clean-up Module and ABEND Dump Formatting Routine must be link-edited into SYS1.LPALIB.

IMSESA.RESLIB must be APF authorized.

8.1.3Data Base Descriptor (DBD)

1Automatic field start calculation

Must code START= in the IMS/ESA DBD.

2Automatic segment length calculation Must code BYTES= in the IMS/ESA DBD.

3FBA DASD Support

MVS does not support FBA (FIXed Block Architecture) DASD devices. This requires changing the DEVICE= parameter of the DATASET statement to the device type that will be used.

4ACCESS Statement

The ACCESS statement is not supported in IMS/ESA. All parameters of the ACCESS statement have equivalent function through parameters of the DBD. This is provided in either DL/I or IMS/ESA DBDs. Therefore, the DBD should be used for portability between DL/I IMS/ESA. The three types of ACCESS statements and the required changes are:

￿HDAM DB

Access Stmt.

DBD equivalent (DL/I or IMS/ESA)

R M R T M =

RMNAME= (module,

CIANPT

# of root anchor points,

P R I M C I =

# of CIs in root addressable area,

RILIM

record insert limit in bytes)

S E G M =

data base root implied

SEQFLD=

SEQFIELD of root implied if PARENT=0 is coded

SEQVAL=

third subfield of the NAME parameter in the FIELD

 

statement defining the sequence field

￿Primary Index of HIDAM DB

Access Stmt.

DBD equivalent (DL/I or IMS/ESA)

R E F =

separate DBD with ACCESS=INDEX needed

S E G M =

NAME= of LCHILD in index DBD

SEQFLD=

INDEX= of LCHILD in index DBD

In addition an LCHILD must be coded in the data DBD referencing an index DBD.

￿Secondary Index for HD DB

Access Stmt.

DBD equivalent (DL/I or IMS/ESA)

R E F =

separate DBD with ACCESS=INDEX needed

SEGM=target seg

determined by which SEGM the LCHILD and XDFLD

follow in data DBD

SEQSEG=source seg

SEGMENT= of XDFLD

170VSE to OS/390 Migration Workbook

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IBM OS/390 manual MVS System Requirements, Data Base Descriptor DBD, Primary Index of Hidam DB, Secondary Index for HD DB

OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.