13.2.2.3 RCB/ENQ/DEQ Macros, Step Systems

as complete. This number may be less than or equal to the number of ECBs specified in the macro.

13.2.2.3 RCB/ENQ/DEQ Macros

This set of macros enables you to protect data files or other resources when processing a multitasking environment.

The VSE RCB macro generates an aligned doubleword resource control block that functions much like an ECB. The VSE ENQ and DEQ macros test the status of the resource through the RCB name.

MVS does not require or use an RCB macro. MVS generates an entry, within the supervisor, which is used in a control area by the ENQ and DEQ macros to test the resource status. Because the MVS entries are stored, tested, and modified within the supervisor, you can protect resources across address spaces. VSE can only protect resources within a partition because the area used to contain the resource status is within the application program area.

	VSE	ENQ rcbname
		(0)

	qname address		,	rname address,	E
		(2-12)		(2-12)	S
	rname lengh		,	SYSTEM ,...
MVS ENQ (2-12)				STEP
				SYSTEMS

Under VSE you can specify only one resource in each ENQ.

The MVS ENQ macro offers many additional facilities. The ENQ macro requests the control program to assign control of one or more serially reusable resources to the active task. If any of the resources are not available, the active task is placed in the wait state until all of the requested resources are available. The qname and rname parameters, roughly equivalent to the VSE rcb name, represent names of a common resource to the control program. These names may or may not have any relation to the actual name of the resources.

The control program does not associate the name with the actual resource. It merely processes requests having the same qname and rname on a first-in, first-out basis. It is your responsibility to associate these names with the actual resource. These parameters may define a resource name pertaining to this step only, or a resource name that may be denoted throughout the entire system.

	VSE	DEQ	rcbname
			(0)

	qname address		,	rname address
		(2-12)		(2-12)
MVS DEQ rname lengh			,	STEP ,...
		(2-12)		SYSTEM
				SYSTEMS

The parameters and additional facilities available under MVS are similar to those explained under the ENQ macro.

286VSE 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 13.2.2.3 RCB/ENQ/DEQ Macros, Step Systems, System Systems

Models: OS/390

13.2.2.3 RCB/ENQ/DEQ Macros

SYSTEM ,...

STEP

SYSTEMS

SYSTEM

SYSTEMS

286VSE to OS/390 Migration Workbook

OS/390 specifications