Steps for diagnosing Tier 1 z/OS sysplex distribution problems

For an in-depth explanation of distribution to Tier 1 z/OS® targets, see the "Sysplex distribution optimizations for multitier z/OS workloads" section in z/OS Communications Server: IP Configuration Guide.

For Tier 1 sysplex distribution

On the Tier 1 distributor, run the Netstat VIPADCFG/-F DETAIL command to see the Tier 1 configuration statement information.

In the VIPA DEFINE section of the report, verify the new flag field, 1, which indicates that this is a VIPA definition for a Tier 1 DVIPA.

In the VIPA DISTRIBUTE section, verify the Tier 1 configuration parameters.

The flag fields show that the targets are Tier1, and that the distribution method uses Server-specific WLM weights (ServerWLM).

The group name is CICSGROUP. The group name is used when a Tier 2 sysplex distributor is being used to correlate Tier 1 targets with their Tier 2 targets. This is explained further in the following Tier 2 distribution.

Dynamic VIPA Information:                                                    
VIPA Define:                                
  IpAddr/PrefixLen: 203.1.181.10/24         
    Moveable: Immediate  SrvMgr: No  Flg: 1 

VIPA Distribute:                                       
  Dest:        203.1.181.10..10000                     
    DestXCF:   ALL                                     
      SysPt:   No   TimAff: No    Flg: ServerWLM Tier1 
      OptLoc:  No                                      
      GrpName: CICSGROUP                              
      ProcXcost:                                       
        zAAP: 001  zIIP: 001                           
      ILWeighting: 0

Run the Netstat VDPT/-O report to see the status of the tier 1 targets. Verify that weight recommendations are nonzero values and that there is a ready server for each tier 1 target. This information is updated in each polling interval. The ready count is 1 for each tier 1 target, which indicates that each has a server listening on port 10000.

Dynamic VIPA Destination Port Table for TCP/IP stacks:  
Dest:        203.1.181.10..10000                        
  DestXCF:   193.1.1.108                                
  TotalConn: 0000000000  Rdy: 001  WLM: 16  TSR: 100    
  Flg: ServerWLM, Tier1                                 
Dest:        203.1.181.10..10000                        
  DestXCF:   193.1.1.181                                
  TotalConn: 0000000000  Rdy: 001  WLM: 08  TSR: 100    
  Flg: ServerWLM, Tier1

Tier 2 sysplex distribution

A Tier 1 target might distribute connections to Tier 2 targets using a Tier 2 sysplex distributor.
In the VIPA DEFINE section of the report, the flag field, "2", indicates that this is a VIPA definition for a Tier 2 DVIPA.
Each Tier 2 distributor will send the weight of each ready server to the Tier 1 distributor; the group name is used to correlate a group of Tier 1 targets with their Tier 2 targets.
OPTLOCAL has been configured (OptLoc: Yes). As connection requests received are received from the Tier 1 targets, Tier 2 distribution targets on the same stack as the Tier 1 target will be preferred.

On each Tier 2 distributor run the Netstat VIPADCFG/-F DETAIL report to verify the following:

The same group name is used on the Tier 1 and corresponding Tier 2 VIPADISTRIBUTE statements. In the example display from the VIPA distribute section, the group name "CICSGROUP" matches the Tier 1 group name.
OPTLOCAL has been configured

VIPA Define:                                   
  IpAddr/PrefixLen: 203.2.108.10/24            
    Moveable: Immediate  SrvMgr: No  Flg: 2     
VIPA Distribute:                                        
  Dest:        203.2.108.10..10002                      
    DestXCF:   ALL                                      
      SysPt:   No   TimAff: No    Flg: ServerWLM Tier2  
      OptLoc:  Yes                                       
      GrpName: CICSGROUP                               
      ProcXcost:                                        
        zAAP: 001  zIIP: 001                            
      ILWeighting: 0

On each tier 2 distributor, run the Netstat VDPT/-O report to see the status of each tier 2 target. In the example, there is a nonzero ready count of 1 for the server on destination XCF 193.1.1.108 and the normalized server-specific weight for this target is 16. There is not a ready server on the destination XCF 193.1.1.181. As the tier 1 distributor receives the tier 2 weights, it adds the weight of the corresponding XCF address. The tier 1 normalized weight for the server on destination XCF 193.1.1.108 is twice that of the server weight on destination XCF 193.1.1.181 because the tier 2 distributor did not have a ready server on destination XCF 193.1.1.181.
```
Dynamic VIPA Destination Port Table for TCP/IP stacks: 
Dest:        203.2.108.10..10002                       
  DestXCF:   193.1.1.108                               
  TotalConn: 0000000000  Rdy: 001  WLM: 16  TSR: 100   
  Flg: ServerWLM, Tier2, OptLocal                      
Dest:        203.2.108.10..10002                       
  DestXCF:   193.1.1.181                               
  TotalConn: 0000000000  Rdy: 000  WLM: 00  TSR: 100   
  Flg: ServerWLM, Tier2, OptLocal 
```