CICS

Online transactions, the communication area, and response handling.

Part of the BankTS language reference.

CICS

An online transaction is declared with cics:

cics transaction accountEnquiry(enquiry: EnquiryCommarea, audit: AuditEntry) {
  enquiry.caBalance = 0.00;
  enquiry.caReturnCode = "00";

  link "AUDITLOG" commarea audit resp linkResp;

  if linkResp == 0 {
    syncpoint resp commitResp;
  } else {
    rollback resp rollbackResp;
  }
}

A CICS transaction receives input through DFHCOMMAREA in the LINKAGE SECTION and ends with EXEC CICS RETURN rather than GOBACK.

The commarea is the first record parameter, and it is how the transaction answers. CICS gives a program one communication area, not one in and one out: DFHCOMMAREA is the caller's own storage, so the request fields and the reply fields are the same block. The generated program moves it in on entry and back out before it returns:

           IF EIBCALEN < LENGTH OF DFHCOMMAREA
               EXEC CICS ABEND ABCODE("BKNC") END-EXEC
           END-IF
           MOVE DFHCOMMAREA TO ENQUIRY-COMMAREA
           ...
           MOVE ENQUIRY-COMMAREA TO DFHCOMMAREA

Every other record parameter is working storage, and working storage is gone when the task ends. A transaction that computes its answer into a second record named something like reply returns control having changed nothing the caller can see — it hands back the bytes it was sent. BANK-CICS-005 refuses it. The EIBCALEN test is IBM's rule rather than a nicety: reading a commarea the caller did not pass, or one shorter than the record expects, reads storage belonging to something else and reads clean.

A transaction ending in returnTransid is the exception. That command carries its own commarea to the next half of the pseudo-conversation, so the compiler appends no writeback and BANK-CICS-005 does not apply.

Beyond link, syncpoint, and rollback:

readFile    "ACCTFILE" into row  key request.accountId resp readResp;
writeFile   "ACCTFILE" from row  key request.accountId resp writeResp;
rewriteFile "ACCTFILE" from row  resp writeResp;

writeQueue "ENQLOG" from row resp writeResp;
readQueue  "ENQLOG" into row resp readResp;

returnTransid "ENQ2" commarea request;

A CICS file command reaches a VSAM dataset through the region rather than through COBOL file control: there is no open, no close, and no FD, because CICS owns the dataset and the program only asks. A read or write names the key it addresses; a rewrite does not, because it updates the record the preceding read is holding and naming a key would describe a different operation.

Temporary storage is the scratchpad an online transaction passes state through. A queue command is ordinary work rather than a commit boundary, so unlike a syncpoint it is allowed inside a loop.

returnTransid ends the task naming what runs next, which is how a pseudo-conversation continues: CICS frees the program between the halves and starts the named transaction when the terminal replies. It takes no resp, because there is no response to come back to, and the compiler does not append a second EXEC CICS RETURN after one.

Not yet available: BMS SEND/RECEIVE MAP, START/RETRIEVE, channels and containers, and HANDLE ABEND.

BANK-CICS-003 exists because a syncpoint inside a loop commits or discards partial work on every iteration, which is rarely what a transaction means.

Read this page as Markdown on GitHub →