Defining a couple data set for system logger

The Incident Log task requires that a couple data set be defined for the system logger component of z/OS® to represent the diagnostic log snapshots. If your installation has not already defined the system logger data set, this topic describes the steps for doing so.

How to check if this step is done

To display LOGR couple data sets on a system, enter the following command:

D XCF,COUPLE,TYPE=LOGR

Figure 1 shows the expected results:

Figure 1. Expected results from the D XCF,COUPLE,TYPE=LOGR command

IXC358I  15.15.26  DISPLAY XCF 038                       
LOGR COUPLE DATA SETS                                    
PRIMARY    DSN: UTCXCF.SVPLEX6.LOGRR13.PRI               
           VOLSER: X6CPLP     DEVN: 3D09                 
           FORMAT TOD         MAXSYSTEM                  
           10/21/2012 12:05:59       32                  
           ADDITIONAL INFORMATION:                       
            LOGR COUPLE DATA SET FORMAT LEVEL: HBB7705   
             LSR(2000) LSTRR(1000) DSEXTENT(10)          
             SMDUPLEX(1)                                 
ALTERNATE  DSN: UTCXCF.SVPLEX6.LOGRR13.ALT               
           VOLSER: X6CPLA     DEVN: 3E08                 
           FORMAT TOD         MAXSYSTEM                  
           10/21/2012 12:17:05       32                  
           ADDITIONAL INFORMATION:                       
            LOGR COUPLE DATA SET FORMAT LEVEL: HBB7705   
             LSR(2000) LSTRR(1000) DSEXTENT(10)          
             SMDUPLEX(1)                                 
LOGR IN USE BY ALL SYSTEMS

If this step is not already done

Define or update the system logger couple data set (LOGR CDS) with a large enough log stream records (LSR) value to allow sufficient space for managing the DASD-only log streams that will be created for capturing diagnostic log snapshots. The LSR value must be large enough to allow for two snapshot log streams for each dump recorded in z/OSMF, plus two model log streams, which are used as templates for defining the storage attributes for the snapshots. For information about modifying and reformatting a couple data set, see z/OS MVS Setting Up a Sysplex.

System logger supports shared sysplex-scope (coupling facility resident) log streams and single-system DASD-only log streams, as follows:

Coupling facility (CF) log streams are sysplex-wide in scope; any system in the sysplex can write to these log streams.
DASD-only log streams can be written to by the local system only. When a DASD-only log stream is closed, it can be read from other systems in the sysplex if it resides on DASD that is shared by the other systems in the sysplex.

The system creates DASD-only log streams for the operations log (OPERLOG) and the sysplex logrec diagnostic snapshots. You do not need to predefine the DASD-only log streams. For the model used, see sample job CEASNPLG, which is supplied by IBM® in SYS1.SAMPLIB(CEASNPLG).

Use shared DASD as the target for OPERLOG and logrec snapshots, so that the Incident Log task can access the log snapshots from any system in the sysplex.

In planning the space requirements for your system logger couple data set, plan for two DASD-only log streams per incident. To allow up to 100 incidents, for example, you must allow enough space for 200 log streams.

IBM recommends that you allow space for up to 1000 DASD-only log streams (or 500 incidents). To do so, use the IXCL1DSU format utility, for example:

//FMTLGCDS JOB  MSGLEVEL=(1,1)                                           
//         EXEC PGM=IXCL1DSU                                             
//* S SUBMIT,JOB=LOGGER.ZOS17.JCL(FORMAT17)                              
//* SETXCF COUPLE,ACOUPLE=(LOGGER.OSR13.LARGE.INVNTRY,LOGR3),TYPE=LOGR   
//* SETXCF COUPLE,PSWITCH,TYPE=LOGR                                      
//SYSPRINT DD   SYSOUT=*                                                 
//SYSIN    DD   *                                                        
 DEFINEDS SYSPLEX(PLEX1) DSN(LOGGER.OSR13.LARGE.INVNTRY) VOLSER(LOGR3)   
   DATA TYPE(LOGR)                                                       
     ITEM NAME(LSR)      NUMBER(2000)
     ITEM NAME(LSTRR)    NUMBER(25)                                      
     ITEM NAME(DSEXTENT) NUMBER(15)                                      
     ITEM NAME(SMDUPLEX) NUMBER(1) 
//

If the system logger couple data set lacks sufficient space to contain the diagnostic snapshots, the system issues message CEA0600I to indicate that the log streams could not be created.

To allow the Incident Log task to access diagnostic log snapshots on other systems in the sysplex, the log streams must reside on shared DASD. DASD-only log streams are expected to be written to SMS-managed DASD.

Related information

For more information, see z/OS MVS Setting Up a Sysplex, which explains the following concepts:

DASD-only log streams
Setting up an SMS environment for DASD data sets
Adding the data sets to the GRSRNL inclusion list
Managing system logger log stream data sets
Defining authorization.