Transaction CICS

Transaction in CICS has a great importance which is the unit of work performed and is represented by a 4 char TRANS ID. It is linked to one or more programs and once a transaction is initiated, programs that are defined gets executed. At the time of transction definition, these programs needs to be given/linked.

In simple words Transaction is a Unique code to execute any program under CICS. Program can not be invoked directly by the user. Either transaction is required or it should be invoked by an other program.

When a Transaction is invoked, program associated with that is loaded in to storage and a task gets started.
– PCT is checked to see the associated program.
– PPT checks whether the program is in main storage or on disk. If it is on DISK, it loads the program on to main storage.

How to define a new transaction in CICS:

CEDA transaction is used for defining a transaction in CICS. It has many options in the definition screen, most of these options are default and can be set based on any other existing transaction in the same group/application.
Below is the Sample definition:

CEDA DEFine TRANSaction(TRN1) GROUP(APPGROUP) 
 TRANSaction == TRN1 
 Group == APPGROUP 
 DEScription == TRANSACTION FOR DISPLAYING CUSTOMERS BY ID 
 PROGram == PROG1 
 TWasize ==                           00000 0-32767 
 PROFile = DFHCICST 
 PArtitionset ==
 STAtus == Enabled                    Enabled | Disabled 
 PRIMedsize :0000                     0-65520 
 TASKDATALoc == Below                 Below | Any 
 TASKDATAKey == User                  User | Cics 
 STOrageclear == Yes                  No | Yes 
 RUnaway ==                           System | 0 | 500-2700000 
 SHutdown ==Disabled                  Disabled | Enabled 
 ISolate == Yes                       Yes | No 
 Brexit == 
REMOTE ATTRIBUTES 
 DYnamic == No                        No | Yes 
 ROutable == No                       No | Yes 
 REMOTESystem == 
 REMOTEName == 
 TRProf == 
 Localq ==                            No | Yes 
SCHEDULING 
 PRIOrity == 001                      0-255 TClass : No No | 1-10 
 TRANClass == 
ALIASES 
 ALias ==
 TASKReq = 
 XTRanid = 
 TPName = 
 => 
 XTPname : 
RECOVERY 
 DTimout = No                          No | 1-6800 (MMSS) 
 RESTart == No                         No | Yes 
 SPurge == No                          No | Yes 
 TPUrge == No                          No | Yes 
 DUmp == Yes                           Yes | No 
 TRACe == Yes                          Yes | No 
 COnfdata == No                        No | Yes 
 Otstimeout == No                      No | 0-240000 (HHMMSS) 
INDOUBT ATTRIBUTES 
 ACtion == Backout                     Backout | Commit 
 WAIT == Yes                           Yes | No 
 WAITTime == 00 , 00 , 00              0-99 (Days,Hours,Mins) 
 INdoubt : Backout                     Backout | Commit | Wait 
SECURITY 
 TRACe == Yes                          Yes | No 
 COnfdata == No                        No | Yes 
 Otstimeout == No                      No | 0-240000 (HHMMSS) 
INDOUBT ATTRIBUTES 
 ACtion == Backout                     Backout | Commit 
 WAIT == Yes Yes | No 
 WAITTime == 00 , 00 , 00              0-99 (Days,Hours,Mins) 
 INdoubt : Backout                     Backout | Commit | Wait 
SECURITY 
 RESSec == No                          No Yes 
 CMdsec == No                          No Yes 
 Extsec : No                           No | Yes 
 TRANSec : 01                          1-64 
 RSl : 00                              0-24 | Public 
DEFINITION SIGNATURE 
 DEFinetime : 
 CHANGETime : 
 CHANGEUsrid : 
 CHANGEAGEnt :                        CSDApi | CSDBatch 
 CHANGEAGRel :

Existing transaction definition can be viewed using CEDA
ex: CEDA VIEW TRAN(TRN2) GROUP(appgroup)

There are CICS supplied transactions which are widely used by CICS admins and users.
Refer these list @ https://www.ibm.com/support/knowledgecenter/en/SSGMCP_5.3.0/com.ibm.cics.ts.systemprogramming.doc/topics/dfha726.html