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The XMI server runs in a different address space from FOCUS and the IMS/DB Interface. The two address spaces must establish a link before they can communicate with one another. A communication file assists this handshake function by acting as a bulletin board, notifying FOCUS about the XMI server's whereabouts. After the handshake is completed, the communication file plays no role in subsequent message traffic.

You can initiate up to 16 concurrent XMI server jobs, each of which requires its own communication file.

You must now allocate as many communication files as needed, up to sixteen. Dataset names are irrelevant but, for clarity, you can use the names 'prefix.FOCBMP.DATA,' 'prefix.FOCBMP1.DATA,'...'prefix.FOCBMP15.DATA' (these names correspond to the ddnames that users allocate when invoking the Interface). You can make the initial allocations through the IEFBR14 utility or the TSO ALLOCATE command, provided that it can catalog datasets on permanently mounted disk packs.

The following example illustrates the allocation of two communication files using the IEFBR14 utility

//STEP1 EXEC PGM=IEFBR14
//DD1   DD   DSN=prefix.FOCBMP.DATA,DISP=(NEW,CATLG),DCB=BLKSIZE=16,
//           SPACE=(TRK,(l)),VOL=SER=xxx 
//DD2   DD   DSN=prefix.FOCBMP1.DATA,DISP=(NEW,CATLG),DCB=BLKSIZE=16,
//           SPACE=(TRK,(l)),VOL=SER=xxx 

where:

prefix

Is the high-level qualifier for your site's FOCUS production datasets.

xxx

Is a valid volume id for your site.

Note that the minimum possible amount of space is allocated. Users must have read access to the communication files.

At execution time, each XMI server job allocates a different communication file to ddname FOCBMP:

//FOCBMP DD DSN=prefix.FOCBMP1.DATA,DISP=SHR

In order for all users to execute a common CLIST, each user program accessing the XMI server should allocate all communication files, to ddnames FOCBMP, and FOCBMP1 through FOCBMP15:

ALLOC F(FOCBMP)  DA('prefix.FOCBMP.DATA') SHR 
ALLOC F(FOCBMP1) DA('prefix.FOCBMP1.DATA') SHR  
  .
  .
  .
ALLOC F(FOCBMP15) DA('prefix.FOCBMP15.DATA') SHR  

You can use any of the sixteen reserved ddnames, and you can pair them with any of the dataset names. However, all of the communication files must be allocated in SHR mode, both by the user and by the XMI server job.

Note: When running MSO, it is recommended that you allocate all communication files in the MSO server JCL.

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The JCL to use for initiating an XMI server job varies depending on whether IMS or CICS has control of the databases and whether the databases are online or local. In addition, XMI server jobs differ in two ways:

• The PSB name, which is user-selected and is passed to the job as a parameter.
• The communication file, which is a different file in each XMI server job but is always allocated to ddname FOCBMP.

The job class and time expiration parameters used with the XMI server job must allow for a long residence in the system, and the priority should be sufficiently high to give good response to the users being serviced. In setting the various job parameters that affect response, remember that these jobs spend most of their time in the WAIT state consuming no resources, since they have nothing to do when not responding to DL/I calls. Even when processing such calls, they only do minimal work. All the logical work of the Interface is done in the various TSO or MSO address spaces.

To prepare JCL for an XMI server job, consult Environments; it describes the various options available and provides JCL for each option. The following is one example

//XMIBMP   EXEC  PGM=DFSRRC00,PARM='BMP,XMI,psbname'
//STEPLIB  DD    DSN=prefix.FOCLIB.LOAD,DISP=SHR
//         DD    DSN=prefix.IMS.LOAD,DISP=SHR
//         DD    DSN=IMS.RESLIB,DISP=SHR
//FOCBMP   DD    DSN=prefix.FOCBMP.DATA,DISP=SHR
//FOCPSB   DD    DSN=prefix.FOCPSB.DATA(psbname),DISP=SHR
//DFSRESLB DD    DSN=IMS.RESLIB,DISP=SHR
//ERRORS   DD    DSN=prefix.ERRORS.DATA,DISP=SHR
//SYSPRINT DD    SYSOUT=A

where:

prefix

Is the high-level qualifier for your site's FOCUS production libraries.

psbname

Is the member of the FOCPSB dataset that corresponds to the PSB to use.

Note:

• STEPLIB must allocate module XMI and the usual IMS execution time modules.
• Ddname FOCBMP is allocated to one of the communication files discussed in Section D.4.Allocate Communication Files, Allocate Communication Files. It is essential to specify DISP=SHR because this file is also allocated by users when they invoke the Interface.
• Ddname FOCPSB is allocated to the member of the FOCPSB dataset that corresponds to the PSB selected.
• Ddname ERRORS points to the PDS of FOCUS error messages that contains member FOCIMS. This dataset must be allocated both by the user and by the XMI server job.
• There is no SYSIN file.
• If this job is submitted for databases under control of CICS, you must allocate ddname DFHLIB to the CICS.LOAD library containing the member DFHDRP (see Environments, for changes to the EXEC card). If your site uses authorized libraries, verify that all FOCUS libraries have the required authorizations.
• Most error conditions detected by the XMI server are reflected back to the originating user, where they are issued to the terminal. The SYSPRINT file allocated in the XMI server job will contain only global error messages pertaining to the XMI server environment as a whole, such as open errors on ddname FOCBMP or FOCPSB.

Note: Instructions for terminating an XMI server job are in Environments.

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Prior to bringing IMS down, you must run job XMIKILL (described in Environments) to cancel any XMI servers that were initiated with the parameter BMP.