If the unit containing the front-end server terminates abnormally due to an error, the transaction that was being executed from that front-end server may be placed in uncompleted status. Because uncompleted transactions lock the database, some database referencing or updating may be limited. To resolve an uncompleted transaction, normally the front-end server must be recovered from the error and then restarted. If the abnormally terminated front-end server is a recovery-unnecessary front-end server, HiRDB automatically resolves the uncompleted transaction. This enables you to use another front-end or back-end server to restart database update processing. A unit that contains a recovery-unnecessary front-end server is called a recovery-unnecessary front-end server unit. Figure 10-3 shows the operation depending on whether or not a recovery-unnecessary front-end server is used.
Figure 10-3 Operation based on whether or not a recovery-unnecessary front-end server is used
![[Figure]](figure/zu090021.gif)
Note that HiRDB Non Recover FES is required in order to use recovery-unnecessary front-end servers.
- Advantages
- You can continue online operation using the remaining front-end servers without having to restart the erroneous front-end server.
- Criteria
- We recommend that you use recovery-unnecessary front-end servers in a system that requires non-stop operation 24 hours a day.
- Relationship with other front-end servers
- Place a recovery-unnecessary front-end server on an independent unit.
- A recovery-unnecessary front-end server cannot support a UAP that uses the X/Open XA interface for connection. Specify PDFESHOST and PDSERVICEGRP in the client environment definition and connect such a UAP to a non-recovery-unnecessary front-end server.
- You can execute the pdrplstart and pdrplstop commands even when the recovery-unnecessary front-end server and recovery-unnecessary front-end server unit are inactive.
- Figure 10-4 shows an example of a system configuration using a recovery-unnecessary front-end server.
Figure 10-4 Example of a system configuration using a recovery-unnecessary front-end server
![[Figure]](figure/zu090030.gif)
- A recovery-unnecessary front-end server cannot execute import processing using the two-phase commitment method for the synchronization point processing method (enabled when fxa_sqle is specified in the import system definition commitment_method operand) of the target Datareplicator. To use the two-phase commitment method for the synchronization point processing method of the target Datareplicator, you need to place one or more front-end servers other than the recovery-unnecessary front-end server at the target HiRDB. You also need to set the client environment variables PDFESHOST and PDSERVICEGRP at the target Datareplicator to connect to a front-end server other than a recovery-unnecessary front-end server.
- Relation with other facilities
- Recovery-unnecessary front-end servers cannot use the system switchover facility. To use the system switchover facility with the system, you must specify nouse in the pd_ha_unit operand in the unit control information definitions of the recovery-unnecessary front-end server unit.
- Organization of this subsection
- (1) Setup method
- (2) Notes