Reference Method

VSE

MVS

 

 

 

Relative Track

Assumed if DSKXTNT is

Assumed if OPTCD does not

Addressing

specified. RELTYPE=HEX

contain R or A. The field

 

(the default) requires the

pointed to by blockaddress

 

hexadecimal form TTTR.

must contain TTR. There is

 

RELTYPE=DEC requires the

no equivalent to RELTYPE

 

zoned decimal for

=DEC in MVS. The form

 

TTTTTTTTRR. In both cases,

must be converted to

 

the R byte(s) must contain

hexadecimal.

 

the actual record number of

 

 

the record on the track.

 

 

 

 

Relative Block

No equivalent.

Assumed if MACRF contains

Addressing

 

I and OPTCD contains R. The

 

 

field pointed to by

 

 

blockaddress must contain

 

 

BBB (binary). The address of

 

 

the first record is 000.

 

 

 

Actual Physical

Assumed if DSKXTNT is not

Assumed if OPTCD contains

Addressing

specified. The address must

an A. The field specified by

 

be in the form MBBCCHHR.

blockaddress must contain

 

The R is ignored.

MBBCCHHR. The M byte is

 

 

different in VSE and MVS.

 

 

See the description of the M

 

 

byte under Track and Record

 

 

Addressing.

 

 

 

Figure 42. Record Reference by ID in VSE and MVS

Record Reference by KEY

Under VSE, records can be referenced by key when you specify READKEY and/or WRITEKEY in the DTFDA. Before the WRITE macro is executed, the field specified by KEYARG in the DTFDA must contain the key of the record for which you search. The field specified by SEEKADDR must contain the track address. If you specify KEYARG, a record with that must already exist on the track or else a no record found condition occurs.

Under MVS, records can be referenced by key when you specify MACRF=(...K...) in the DCB and the type parameter of the READ,WRITE macro contains K. The field specified by keyaddress in the READ/WRITE macro must contain the actual key of the record for which you search. Blockaddress contains the search start address (see Figure 43 on page 318).

Chapter 13. A s s e m b l e r 317

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IBM OS/390 manual Record Reference by KEY, Reference Method
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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.
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