Advanced Topics › Communication Methods › Cross-system Communication Methods › Virtual Control File Communication Methods › CTCDASD Communication Method › How You Implement the CTCDASD Communication Method

How You Implement the CTCDASD Communication Method

To implement the CTCDASD communication method, you customize certain parameters in the MIMINIT member.

To select the CTCDASD communication method

In the MIMINIT member,

1. Issue the following command:

   DEFSYS (sysa,aa,sysa),(sysb,bb,sysb)
   

   This command defines all systems participating in the MIMplex.

2. Issue the following command:

   GLOBALVALUE ANYELIGIBLE=yes/no,
               MOSTPREFERRED=yes/no,
               NOMASTER=wait/term,
               VCFMASTER=(sysa,sysb,...,sysn)
   

   This command defines the VCF recovery options and master candidate list.

3. Issue the following command:

   CTCPATH FROMSYSTEM=sysa ADDRESS=deviceaddress TOSYSTEM=sysb
   

   This command defines the CTC device addresses for use in the MIMplex.

   CTCPATH FROMSYSTEM=sysb ADDRESS=deviceaddress TOSYSTEM=sysa,
   

4. Issue the following command:

   MIMINIT COMMUNICATION=(CTCDASD,INITIAL=CTC/DASD)
   

   The preceding command define thes CTCDASD communication method, and indicates your preferred INITIAL status.

   The INITIAL parameter is unique to the CTCDASD communication method. It indicates your preferred communication method. Once synchronization has completed on the DASD or the coupling facility structure control file, this value determines which communication method to employ:

   • INITIAL=CTC indicates CA MIM is to automatically migrate to a selected VCF master.
   • INITIAL=DASD indicates CA MIM is to continue using the DASD or coupling facility structure control file. If desired, the MIGRATE command can be issued later to migrate to a master VCF system.

   This value is checked after the initial DASD or coupling facility structure control file synchronization, and after any event causing a DASD or coupling facility structure control file re-synchronization.

5. Define the control files to be used in the MIMPROC member:

   //MIMTBL00  DD DSN=MIM.CF00
   //MIMTBL01  DD DSN=MIM.CF01
   

   Alternatively, define the control files to be dynamically allocated in the MIMINIT member:

   ALLOCATE DDNAME=MIMTBL00,DSNAME=MIM.CF00
   ALLOCATE DDNAME=MIMTBL01,DSNAME=MIM.CF01
       or
   ALLOCATE XESFILEID=00 STRNAME=MIM#CF00
   ALLOCATE XESFILEID=01 STRNAME=MIM#CF01
   

6. Define checkpoint files only if you are using the ECMF REQUEUE feature:

   IFSYS sysa
     MIMINIT CHKPTDSN=sysa.dsn
   ENDIF
   IFSYS sysb
     MIMINIT CHKPTDSN=sysb.dsn
   ENDIF
   

   Alternatively, you can use the ALLOCATE command placed in the MIMINIT member to define the checkpoint files to be used by each system:

   IFSYS sysa
     ALLOCATE DDNAME=MIMCKP00,DSNAME=sysa.primckpt
     ALLOCATE DDNAME=MIMCKP01,DSNAME=sysa.altckpt
   ENDIF
   IFSYS sysb
     ALLOCATE DDNAME=MIMCKP00,DSNAME=sysb.primckpt
     ALLOCATE DDNAME=MIMCKP01,DSNAME=sysb.altckpt
   ENDIF
   

Note: For more information, see the Statement and Command Reference Guide.

You can have a combination of both DASD and coupling facility structure control files in a CTCDASD environment.