Notes:

1. The codes are as follows:

￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿

￿ VSE ￿MVS (BSAM only)￿

￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿

￿

REW ￿

No equivalen￿. The op￿ion specified in ￿he DISP

￿

￿

RUN ￿

parame￿er of ￿he DD s￿a￿emen￿ is ￿aken. Refer

￿

￿

￿

also ￿o ￿he OPEN/CLOSE op￿ions.

￿

￿

BSR ￿

BSR, number of blocks

￿

￿

FSR ￿

FSR, number of blocks

￿

￿

BSF ￿

BSM Bo￿h of ￿hese codes cause spacing pas￿ ￿apemark,

￿

￿

FSF ￿

FSM ￿hen, spacing in ￿he opposi￿e direc￿ion over ￿apemark.￿

￿

WTM ￿

No equivalen￿

￿

￿

ERG ￿

 

￿

￿

BSL ￿

No equivalen￿

￿

￿

FSL ￿

 

￿

￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿￿

2.Under MVS, if the forward or backspace operation does not complete successfully, control is passed to the error analysis routine (SYSAD). If you do not specify a SYNAD routine, the task terminates abnormally.

3.If a tapemark is encountered for DSR or FSR, control is returned to the processing program, and register 15 contains a count of the uncompleted forward spaces or backspaces. If the operation completes normally, register 15 contains zero.

4.If you specify OPTCD=H in the data control block, the CNTRL macro instruction can perform record positioning on VSE tapes that contain embedded checkpoint records. Imbedded checkpoint records encountered during the record positioning are bypassed and are not counted as blocks spaced over. You must also specify OPTCD=H in a JCL DD statement. The CNTRL macro instruction cannot be used to backspace VSE 7-track tapes that are written in data convert mode that contain embedded checkpoint records (BSAM).

NOTE Macro

VSE

NOTE

filename

 

 

(1)

 

 

 

MVS

NOTE

dcbaddress

 

 

(1-12)

 

 

 

The result of the NOTE macro is the same in VSE and MVS. Information is returned in register 1 in the format 0bbb. If you use NOTE under MVS, the tape on which the data set resides must have standard labels if the OPEN option RDBACK or DISP=MOD has been specified. The MVS NOTE macro is valid only for BSAM and BPAM.

POINTW / POINTR Macros

VSE

POINTW

filename

 

 

POINTR

(1)

 

 

 

 

 

MVS

POINT

dcbaddress

, blockaddress

 

 

(1-12)

(2-12)

 

 

 

(0)

 

 

 

 

Chapter 13. A s s e m b l e r 299

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IBM OS/390 VSE MVS Bsam only, No equivalen. The opion specified in he Disp, BSR, number of blocks, FSR, number of blocks

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.