Defining coupling-facility structures for log streams

You have to define log structures in two places: the coupling facility resource management (CFRM) policy and the system logger LOGR policy. Use the DEFINE STRUCTURE keyword of the ICXMIAPU utility to define the coupling facility structures needed for all the log streams that your DFSMStvs instances will use. Define structures in the LOGR policy in the system logger couple data sets.

Related reading: For details on how to code the ICXMIAPU utility, see z/OS MVS Setting Up a Sysplex.

Use the CFRM policy to divide coupling facility space into structures. The CFRM policy enables you to define how MVS™ should manage coupling facility resources. Figure 1 shows the beginning of the definition of a CFRM policy:

Figure 1. Sample definition of the CFRM policy

//RLSPOL01 JOB CLASS=A,MSGCLASS=H,                                    
//         MSGLEVEL=(1,1),REGION=4096K,TIME=1440                      
//******************************************************************* 
//* This job defines the CFRM policy. Log structures are only part    
//* of it. This contains the structures for all the TVS logs and the  
//* RRS logs. The structures must have also been defined to the       
//* logger policy.                                                    
//******************************************************************* 
//*                                                                   
//* UPDATE THE ADMINISTRATIVE POLICY DATA IN THE COUPLE DATA SET      
//* FOR COUPLING FACILITY RESOURCE MANAGER (CFRM)                     
//*                                                                   
//******************************************************************  
//STEP20   EXEC PGM=IXCMIAPU                                          
//*STEPLIB  DD   DSN=SYS1.MIGLIB,DISP=SHR                             
//SYSPRINT DD   SYSOUT=H                                              
//SYSIN    DD   *                                                     
     DATA TYPE(CFRM)                                                  
     DEFINE POLICY NAME(RLSPOL01) REPLACE(YES)                        
                                                                      
       STRUCTURE NAME(OPERLOG_STR     )                               
                 SIZE(60512)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
                                                                      
       STRUCTURE NAME(LOG_DFHLOG_001  )                               
                 SIZE(10240)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
       STRUCTURE NAME(LOG_DFHLOG_002  )                               
                 SIZE(10240)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
       STRUCTURE NAME(LOG_DFHLOG_003  )                               
                 SIZE(10240)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
       STRUCTURE NAME(LOG_DFHLOG_004  )                               
                 SIZE(10240)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
       STRUCTURE NAME(LOG_DFHSHUNT_001)                               
                 SIZE(10240)                                          
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                       
       STRUCTURE NAME(LOG_DFHSHUNT_002)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_DFHSHUNT_003)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_DFHSHUNT_004)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_USERJRNL_001)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_USERJRNL_002)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_USERJRNL_003)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_USERJRNL_004)                              
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
       STRUCTURE NAME(LOG_GENERAL_001)                               
                 SIZE(10240)                                         
                 PREFLIST(CFSVTX,CFSVTY,CFSVTZ)                      
         /*

Multiple log streams can write data to a single coupling-facility structure. This does not mean that the log data is merged; the log data stays segregated according to log stream. You can specify the number of log streams that use the resources of a single coupling facility structure. Use the LOGSNUM parameter on the IXCMIAPU service to define a structure.

Each log stream is allocated a proportion of the structure space, based on the number of currently connected log streams (up to the limit specified in LOGSNUM). For example, a structure can be defined to contain a maximum of 30 log streams. If only 10 log streams are connected, each log stream can use one tenth of the space in the structure. As other log streams are connected and disconnected, the system logger adjusts the proportion of space to each log stream used.

It is important to plan carefully before specifying a value for LOGSNUM. This parameter determines how much storage space in the structure is available to each log stream. A number in the range 10 to 20 is optimum in many environments.