The daily edition.

1. Capability Overview & Problem It Solves

In IBM mainframe CICS, application execution is strictly governed by Resource Definition Online (RDO) stored in the CICS System Definition (CSD) file (dfhdrdat). Every user interaction initiated by a 4-character transaction identifier (such as ACCT, PAY1, or INQ2) requires a registered transaction definition. This definition determines the initial program entry point, execution priority, timeout thresholds, task work area allocations, and concurrency throttling.

Similarly, application load modules require corresponding program definitions specifying the language runtime, memory residency, and remote routing properties.

Rocket Enterprise Server delivers full mainframe-compatible CICS Resource Definition (RDO) emulation (CICS Resource Definitions - Rocket Software Documentation). Organizations can migrate their mainframe CSD decks directly into Enterprise Server, administer definitions interactively through ESMAC and ESCWA, or automate batch resource updates using standard command-line tools—executing transactions without altering application calling conventions.

2. Architecture & How It Works

• DEFINE TRANSACTION & Runtime Dispatching:
  • Program Binding: Maps the incoming 4-character TRANSID to its target entry module (PROGRAM).
  • Concurrency Throttling with TRANCLASS: Associates transactions with a transaction class (TRANCLASS) that enforces maximum concurrent active tasks (MAXACTIVE) and queue limits (PURGETHRESH). This prevents resource-intensive batch queries from monopolizing Service Execution Processes (SEPs) and starving high-priority interactive online transactions.
  • Transaction Work Area (TWASIZE): Allocates a dedicated contiguous memory block (0 to 32,767 bytes) automatically provisioned at task initiation and accessible across all programs in the task execution chain via EXEC CICS ADDRESS TWA.
  • Abend Protection & Timeouts: The RUNAWAY parameter sets runaway CPU loop detection thresholds (forcing an AICA abend if exceeded), while DTIMOUT triggers automatic task cancellation during deadlocks or stalled resource waits.
• DEFINE PROGRAM & Dynamic Lifecycle Management:
  • Module Specification: Declares program characteristics (LANGUAGE(COBOL), STATUS(ENABLED)).
  • Dynamic Reloading vs. Residency (RELOAD): Specifies whether a fresh copy of the program module is loaded on every invocation or kept resident in shared memory.
  • Zero-Downtime Deployment via NEWCOPY: Administrators can issue CEMT SET PROGRAM(name) NEWCOPY or PHASEIN to hot-swap compiled application binaries (.gnt or .so) across all active SEPs without restarting the region.
  • Transparent Remote Routing: Setting REMOTE(YES) and designating a REMOTESYSTEM(sysid) instructs Enterprise Server to automatically route EXEC CICS LINK calls to a remote region using Distributed Program Linking (DPL) without modifying COBOL application code.
• Resource Groups & System Startup Lists:
  • Individual resource definitions are organized into logical Groups (e.g., ACCTGRP, PAYGRP).
  • A region's System Initialization Table (SIT) references a Startup List (_STARTUPLIST), which determines the exact sequence of resource groups automatically installed into active shared memory when the region initializes.

3. Key Syntax, Configuration & Operational Directives

1. Batch CSD Definition Deck (casrd / dfhcsdup): Mainframe CSD extract definitions can be loaded directly into the Enterprise Server resource catalog (dfhdrdat) using the casrd utility:

* Define a resource group for payroll
DEFINE GROUP(PAYROLL)

* Define transaction class to throttle concurrent executions
DEFINE TRANCLASS(PAYCLS) GROUP(PAYROLL)
       MAXACTIVE(5)
       PURGETHRESH(50)

* Define the transaction
DEFINE TRANSACTION(PAY1) GROUP(PAYROLL)
       PROGRAM(PAYPROC)
       TRANCLASS(PAYCLS)
       TWASIZE(512)
       DTIMOUT(30)
       RUNAWAY(5000)

* Define the underlying COBOL application program
DEFINE PROGRAM(PAYPROC) GROUP(PAYROLL)
       LANGUAGE(COBOL)
       STATUS(ENABLED)
       RELOAD(NO)

2. Dynamic Program Refresh via CEMT: Operators can refresh or enable components dynamically inside a running region from a 3270 terminal or ESMAC:

CEMT SET PROGRAM(PAYPROC) NEWCOPY
CEMT SET TRANSACTION(PAY1) ENABLED

3. Accessing the Transaction Work Area (TWA) in COBOL:

       LINKAGE SECTION.
       01  TWA-DATA.
           05  TWA-USER-ID       PIC X(8).
           05  TWA-TERM-ID       PIC X(4).
           05  TWA-START-TIME    PIC 9(8) COMP.
       ...
       PROCEDURE DIVISION.
           EXEC CICS ADDRESS
                TWA(ADDRESS OF TWA-DATA)
           END-EXEC.

4. Reference Citations (Rocket Enterprise Server 12.0 Manuals)

• CICS Resource Definitions - Rocket Software Documentation — Enterprise Server 12.0 for UNIX
• CICS Resource Definitions - Rocket Software Documentation — Enterprise Server 12.0 for Windows
• CICS Resource Definitions - Rocket Software Documentation — Enterprise Test Server 12.0