Creating an alias transaction for an Atom feed

An alias transaction handles the later stages of processing for an Atom feed. CICS® supplies a resource definition for a default Atom feed alias transaction, CW2A. Set up a TRANSACTION resource definition if you want to define an alternative alias transaction.

About this task

For non-Atom HTTP requests handled by CICS web support, you only use an alias transaction when a user-written application program handles the requests. However, for Atom feeds, an alias transaction is used for processing all requests, whether or not a user-written service routine is involved.

You might want to use alternative alias transaction names for these purposes:

Auditing, monitoring or accounting
Modifying resource and command security settings
Allocating initiation priorities
Allocating Db2® resources
Assigning different runaway values to different CICS application programs
Transaction class limitation

You can set up as many alias transaction definitions as you want. You can use the URIMAP definition to specify the alias transaction that is required for a particular request.

CW2A specifies RESSEC(YES) and CMDSEC(YES), meaning that if resource and command security is active for the CICS region, it is applied to this transaction. If you specify resource and command security for your alias transaction, you will need to give web clients appropriate permissions to access the resources and commands used by the transaction. For more information about security for Atom feeds and collections, see Security for Atom feeds.

Follow the instructions in TRANSACTION resource definitions to create a transaction resource definition. When you are following these instructions, note these points:

Procedure

Base your alias transaction definition on the definition of CW2A, making any changes that you require.

Here is the definition of CW2A:

DEFINE TRANSACTION(CW2A)   GROUP(DFHWEB2)
       PROGRAM(DFHW2A)     TWASIZE(512)
       PROFILE(DFHCICST)   STATUS(ENABLED)
       TASKDATALOC(ANY)    TASKDATAKEY(CICS)
       RUNAWAY(SYSTEM)     SHUTDOWN(DISABLED)
       PRIORITY(1)         TRANCLASS(DFHTCL00)
       DTIMOUT(NO)         TPURGE(NO)        SPURGE(YES) 
       RESSEC(YES)         CMDSEC(YES)
       DESCRIPTION(CICS Web2.0 Atomservice alias transaction)

Your alias transaction definition must use the CICS-supplied alias program DFHW2A.
The alias program accesses the user-written service routine or CICS resource that is named in the ATOMSERVICE definition.
Your alias transaction definition must be a local transaction.
Your alias transaction must have a transaction work area size (TWASIZE) of at least 512-bytes.
Make sure the priority of the alias transaction is equal to, or higher than, the priority of the transactions associated with web attach tasks, such as CWXN.
Priorities for CICS web support transactions (CWXN, CWXU, CWBA, CW2A) explains why this is important.
Atom feed requests might qualify for being processed by directly attached user transactions, and bypassing the web attach task. Performance enhancement is gained by saving the CPU time needed for processing requests. For more information, see Processing HTTP requests by using directly attached user transactions.