Communication Region | IBM OS/390 specs

When this program received control from MVS

Reg. 13 contained address of MVS save area.

Reg. 14 contained address of MVS return.

Reg. 15 contained address of this program′s entry point.

PROGA	START
	SAVE	(14,12),,*	Store Regs in MVS save area
+	B	10(,15)
+	DC	AL1(5)
+	DC	CL5′ PROGA′

+STM 14,12,12(13)

	LR	12,15	Load start address in Reg 12
	USING PROGA,12		Define Reg 12 as base reg
	ST	13,SAVEIT+4	Store address of MVS save
*			area in PROGA′ s save area
	LA	11,SAVEIT	Load address of this Program
*			save area into Reg 11
	ST	11,8(13)	Store address of PROGA′ s save
*			area in MVS save area
	LR	13,11	Load Reg 13 to point to this
	.
APPLICATION PROGRAMMER LOGIC
	.
	L	13,SAVEIT+4	Load address of MVS save area
*			into Reg 13
	RETURN (14,12),RC=0 Restore registers and branch
*			to MVS Return Address
+	L	14,12(,13)	Restore Register 14
+	LA	15,0	Load Return Code
+	LM	0,12,20(13)	Restore the registers
+	BR	14	Return
SAVEIT	DC	18F′ 0 ′

Figure 29. Sample Initiation Termination Coding

13.2.1.3 Communication Region

VSE has a communication region, a storage area within the supervisor, that contains:

∙

The date

The job name

User program communication bytes

User program switch indicators (UPSI)

Problem program area addresses.

MVS does not provide a similar fixed area in the control program. Some of the VSE communication region facilities are available in MVS as explained in the following text.

Date

The VSE macro instruction COMRG provides the address of the communication

274VSE to OS/390 Migration Workbook

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.

IBM OS/390 manual Communication Region

Models: OS/390

11,SAVEIT

SAVEIT

Figure 29. Sample Initiation Termination Coding

13.2.1.3 Communication Region

Date

274VSE to OS/390 Migration Workbook

OS/390 specifications