Connection, disconnection, and inquiry transactions for the CICS DBCTL interface

There are two CICS® transactions that you can use to connect to, disconnect from, and inquire on the status of the CICS-DBCTL interface. They are:

You can enter CDBC and CDBI from either a CICS terminal or an MVS™ console. You can restrict access to these transactions using transaction security. Messages from CDBC can be sent to the transient data destination CDBC. (For help on defining transient data destinations, see CICS Resource Definition Guide.)

CDBC transaction for connect and disconnect

Typing CDBC on a 3270-type terminal displays a menu for connecting CICS to, and disconnecting it from, DBCTL. Figure 11 shows an example of the menu.

To connect to DBCTL, enter option number 1 after:

Option Selection ==>
Figure 11. CDBC transaction menu screen
 CDBC                CICS-DBCTL CONNECTION/DISCONNECTION                  93.259
                                                                        13:39:20
 
           Select one of the following:
 
                1 Connection
                2 ORDERLY disconnection
                3 IMMEDIATE disconnection
 
 
           Option Selection     ==> 2
           Startup Table Suffix ==> 00
           DBCTL ID Override    ==>
 
   DFHDB8209D DBCTL orderly disconnection requested. Press PF5 to confirm.
 
   Status of the Interface: DFHDB8293I DBCTL connected and ready.
               CICS APPLID: IYAHZCD2
                  DBCTL ID: SYS2
      Startup Table Suffix: 00
 
 
 PF1 = Help   2 = Refresh   3 = End
 

If you want to specify a DRA startup table suffix, you can enter it after:

Startup Table Suffix ==>

If you do not specify a suffix, CICS uses the one that was used when it was last connected to DBCTL. If this is the first time you have connected CICS to DBCTL, and you do not specify a suffix, CICS uses the default suffix, which is 00.

If you want to specify a DBCTL identifier, you can enter it after:

DBCTL ID Override ==>

If you do not specify a DBCTL identifier, the DRA uses the DBCTL identifier specified on the DBCTLID parameter in the DRA startup table.

When you have pressed ENTER, you should get the message:

DFHDB8209 I DBCTL orderly disconnection requested. Press PF5 to confirm.

as shown on the example screen in Figure 11.

The CDBC menu screen displays the following additional information:

The DBCTL identifier and the DRA startup parameter table suffix are only displayed when CICS has been connected to DBCTL. You can refresh any of the information on the CDBC menu screen by pressing PF2.

You can obtain a help screen for the CDBC menu by pressing PF1. As you can see in Figure 12, the CDBC help screen reminds you which number to specify for which option, what the options mean, and summarizes the CICS-DBCTL interface information displayed on the CDBC menu screen.

Figure 12. CDBC transaction menu help screen
                  HELP : CICS-DBCTL CONNECTION/DISCONNECTION
 
  To CONNECT to DBCTL, select option 1. You can also specify a startup
   table suffix, or accept the existing suffix. The id of the DBCTL system is
   obtained from the startup table, but can be optionally overridden.
 
  To DISCONNECT from DBCTL, select option 2 or option 3.
 
     Select option 2 for ORDERLY disconnection: this allows all CICS-DBCTL
     transactions from this CICS to complete before disconnecting from DBCTL.
 
     Select option 3 for IMMEDIATE disconnection: this allows all CICS-DBCTL
     requests from this CICS to complete before disconnecting from DBCTL.
  ------------------------------------------------------------------------------
  Displayed information (press PF2 to refresh the information):
     STATUS OF THE INTERFACE The current status of the connection to DBCTL.
     CICS APPLID             The application identifier for this CICS system.
 
     Displayed when available:
     DBCTL ID                 Identifier of the DBCTL system with which this
                              CICS system is communicating.
     STARTUP TABLE SUFFIX     Suffix used when CICS was connected to DBCTL.
 
                   PRESS ENTER TO RETURN TO SELECTION SCREEN

Using CDBC without the menu screen

The menu screen is displayed if you use CDBC from a 3270-type terminal, However, if you issue CDBC from a CRLP or DASD sequential terminal or operating system console, the menu screen is not displayed. For example, if you specify:

CDBC CONnect

DBCTL is connected using the default suffix, 00.

If you specify a suffix:

CDBC CONnect SUFfix(12)

and DBCTL is connected using suffix 12.

You can also type a DBCTL identifier, in addition to the suffix, or on its own. For example, if you enter:

CDBC CONnect DBCtlid(DBC1)

CICS is connected to the DBCTL named DBC1.

You can also enter:

CDBC CONnect DBCtlid(DBC2) SUFfix(11)

or

CDBC CONnect SUFfix(11) DBCtlid(DBC2)

in either case, CICS is connected to DBCTL DBC2, using suffix 11.

See What happens when you have requested connection to DBCTL below for details of the system’s response to your connection request.

If you disconnect CICS from DBCTL using a BSAM CRLP-type terminal, the menu screen is not displayed.

For orderly disconnection, specify:

CDBC DISconnect

For immediate disconnection, enter:

CDBC DISconnect IMMediate

See Deciding whether to use orderly or immediate disconnection for information on the two types of disconnection request.

What happens when you have requested connection to DBCTL

When you have requested connection to DBCTL, you should get messages confirming that connection is taking place. If you have used the CDBC menu, the following messages appear on the terminal:

Status of the Interface: DFHDB8292I DBCTL CONNECT PHASE 2 IN PROGRESS.
Status of the Interface: DFHDB8293I DBCTL CONNECTED AND READY.

If you have not used the CDBC menu, the following messages appear on the MVS console:

+DFHDB8210D CONNECTION TO DBCTL IS PROCEEDING. CHECK CDBC TD QUEUE.
+DFHDB8225I DBDCCICS THE DBCTL ID IS SYS1. THE DRA STARTUP TABLE SUFFIX IS 00.

The CICS Messages and Codes manual contains information about interpreting the CICS DFHDBnnnn messages that are issued when you are using CDBC.

If DBCTL is not yet available, the main CICS-supplied IMS™ control exit, DFHDBCTX, is invoked. DFHDBCTX in turn calls DFHDXAX. For more information about the IMS control exit routines, see the appropriate IMS Customization Guide.

For a DBCTL restart, the control exit is invoked as for any DBCTL connection attempt. However, instead of returning control directly to the DRA, the control transaction invokes the DFHDXAX module. This control exit routine checks to see if it is being invoked for a failing connection:

If an IDENTIFY failed, and CICS is not terminating, the action taken then depends on whether there is an RST defined, which may or may not contain alternative DBCTL IDs.

CICS regions without a recoverable service table (RST)

If there is no RST, DFHDXAX selects the current DBCTL ID, and initiates repeated attempts to reconnect to the current DBCTL, thus avoiding operator intervention.

Retries are made every five seconds for a ten minute period, and message DFHDB8297 is issued periodically. If reconnection is still not successful after ten minutes, DFHDXAX abandons the attempt, and requests IMS to issue message DFS0690A, which requires operator intervention. The IMS Messages and Codes manual manual contains guidance on interpreting the IMS DFSnnnn messages that are displayed when you are using CDBC. If you reply CANCEL, the connection attempt is abandoned. It you reply WAIT, the DRA retries the connection attempt after the number of seconds specified in the TIMER parameter in the DRA startup parameter table. If the connection attempt fails again, the DRA will continue to retry after the same number of seconds. You can stop these repeated connection attempts by using the CDBC transaction to disconnect from DBCTL. (This can be either the same instance of CDBC or one from a different terminal.) Disconnection takes effect when the DRA next tries to reconnect to DBCTL.

CICS regions with an RST

If you are using XRF, and therefore have defined an RST, and it does contain alternative DBCTL IDs to which CICS can try to connect, DFHDXAX selects each DBCTL subsystem ID in the RST in turn as a candidate for reconnection.

The processing, which can take one of two courses, is as described in I/O PCB.

Deciding whether to use orderly or immediate disconnection

Orderly disconnection allows all existing CICS-DBCTL tasks to complete before CICS is disconnected from DBCTL. Tasks not currently using DBCTL are prevented from issuing further PSB schedule requests. This means that there should not be any in-doubt logical units of work (UOWs), and database records are available to other CICS systems connected to that DBCTL.

Immediate disconnection allows only current DL/I requests to DBCTL from this CICS system to complete before CICS is disconnected from DBCTL. Any new DL/I or PSB schedule requests are prevented. This can cause in-doubt UOWs for the task involved and leave database records unavailable for other CICS systems connected to that DBCTL until it is reconnected. What happens depends on the type of request issued to DBCTL after the immediate disconnection request:

So, use immediate disconnection only if necessary. For example, you may need to use it if you have already issued an orderly disconnection request which has not taken place, and you need disconnection to take place soon. Orderly disconnection may be delayed by a task that is issuing many DL/I requests, or by a conversational task that is awaiting input from an unattended terminal. If you think the problem is being caused by such a task, you may prefer to identify it using CEMT INQ TASK, and then use CEMT SET TASK(n) PURGE, where "n" is the task identifier to purge it. You can then use orderly disconnection. However, if the problem is being caused by many tasks or by a single task that you cannot identify, you may have to use immediate disconnection.

CDBI transaction for inquiry

You can use the CDBI transaction to inquire on the status of the DBCTL connection. Typing CDBI displays a screen like the one shown in Figure 13. The CDBI screen shows the status of the CICS-DBCTL interface (in this example, DBCTL is connected and ready), plus the APPLID of the CICS system (DBDCCICS) and the DBCTL identifier (SYS1). You can refresh the information by pressing PF2.

Figure 13. CDBI transaction screen
 CDBI                     CICS-DBCTL INTERFACE INQUIRY             93.194
                                                                 11:23:50
             Status     : DFHDB8293 I DBCTL connected and ready.
             CICS APPLID: DBDCCICS
             DBCTL ID   : SYS1
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 PF1 = Help   2 = Refresh   3 = End
 

You can obtain a help screen for CDBI by pressing PF1. Figure 14 shows an example of such a panel. The CDBI help screen tells you how to refresh the information on the CDBI screen, and explains that information. It includes a list of the CICS messages describing the status of the CICS-DBCTL interface that can appear on the CDBI screen. The CICS Messages and Codes manual tells you how to interpret these messages.

Figure 14. CDBI transaction help screen
                      HELP : CICS-DBCTL INTERFACE INQUIRY
  The CICS-DBCTL interface inquiry screen shows:
    STATUS OF THE INTERFACE    The status can be:
      DFHDB8290I DBCTL NOT CONNECTED TO CICS.
      DFHDB8291I DBCTL CONNECT PHASE 1 IN PROGRESS.
      DFHDB8292I DBCTL CONNECT PHASE 2 IN PROGRESS.
      DFHDB8293I DBCTL CONNECTED AND READY.
      DFHDB8294I DBCTL ORDERLY DISCONNECT IN PROGRESS.
      DFHDB8295I DBCTL IMMEDIATE DISCONNECT IN PROGRESS.
      DFHDB8296I DBCTL CANNOT BE CONNECTED TO CICS.
    CICS APPLID  The application identifier of this CICS system.
  Displayed when available:
    DBCTL ID     The identifier of the DBCTL system with which this CICS
                 is communicating
  You can press PF2 to update (refresh) the information shown on the screen
 
 
 
 
 
 
 
                   PRESS ENTER TO RETURN TO INQUIRY SCREEN

Related concepts
Operations with DBCTL
Connecting to DBCTL: overview
Connecting DBCTL to CICS automatically
Operator communication with DBCTL -- overview
Dealing with messages from DBCTL and CICS
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