Hot standby configuration example

The following example shows configuration for the hot standby distribution method:

VIPADISTRIBUTE DISTMETHOD HOTSTANDBY AUTOSWITCHBACK HEALTHSWITCH
   9.67.240.02 PORT 10000
   DESTIP
      203.3.10.16   PREFERRED
      203.3.10.17   BACKUP    50
      203.3.10.18   BACKUP   100

Because server 203.3.10.16 is the preferred server and AUTOSWITCHBACK is configured, that server becomes the active target when it enters the listening state. Servers 203.3.10.17 and 203.3.10.18 are the backup servers. The highest ranked backup server (203.3.10.18) becomes the active server if server 203.3.10.16 becomes unavailable.

Use the Netstat VIPADCFG/-F command to display the configuration:

Dynamic VIPA Information:                                      
⋮                             
  VIPA Distribute:                                             
    Dest:      9.67.240.02..10000                             
      DestXCF: 203.3.10.16                                     
      DistMethod: HotStandby      SrvType: Preferred           
      AutoSwitchBack: Yes         HealthSwitch: Yes                 
      SysPt:   No   TimAff: No    Flg:                         
      OptLoc:  No                                              
    Dest:      9.67.240.02..10000                             
      DestXCF: 203.3.10.17                                     
      DistMethod: HotStandby      SrvType: Backup  Rank: 050   
      AutoSwitchBack: Yes         HealthSwitch: Yes                 
      SysPt:   No   TimAff: No    Flg:                         
      OptLoc:  No 
    Dest:      9.67.240.02..10000                             
      DestXCF: 203.3.10.18                                    
      DistMethod: HotStandby      SrvType: Backup  Rank: 100   
      AutoSwitchBack: Yes         HealthSwitch: Yes                 
      SysPt:   No   TimAff: No    Flg:                         
      OptLoc:  No

Use the Netstat VDPT/-O command to display the status of the servers:

Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.16                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 10 TSR: 100 
  DistMethod: HotStandby           SrvType: Preferred                     
  Flg: Active
Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.17                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 10 TSR: 100 
  DistMethod: HotStandby           SrvType: Backup                     
  Flg: Backup 
Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.18                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 10 TSR: 100 
  DistMethod: HotStandby           SrvType: Backup                     
  Flg: Backup

The Active and Backup flags show the current status of each server. For example, the preferred server (203.3.10.16) is displayed with the Active flag, indicating that it is the active server. Each server uses a default WLM weight of 10 for displays and health calculations.

If the active server becomes unavailable for some reason, the Netstat VDPT/-O command displays something similar to the following status:

Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.16                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 00 TSR: 000 
  DistMethod: HotStandby           SrvType: Preferred                     
  Flg: Backup
Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.17                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 10 TSR: 100 
  DistMethod: HotStandby           SrvType: Backup                     
  Flg: Backup 
Dest:        201.2.10.15..5000                                            
  DestXCF:   203.3.10.18                                                 
  TotalConn: 0000000000  Rdy: 001  WLM: 10 TSR: 100 
  DistMethod: HotStandby           SrvType: Backup                     
  Flg: Active

The target server responsiveness (TSR) value for server 203.3.10.16 dropped to zero (TSR: 000), and the distributor switched to use the highest ranked backup, 203.3.10.18 (configured with a Backup rank of 100). The backup target becomes the active target (Flg: Active), and the preferred target becomes a backup target (Flg: Backup). However, because the switch from the preferred target occurred because the TSR value is 0, even when the TSR begins to recover, automatic switchback to this target does not occur. If server 203.3.10.16 is quiesced and resumed, the distributor can switch distribution back to this preferred server.