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Partition Management
3.6 Managing Partitions
•
rtr_partition_fail_to_shadow
•
rtr_partition_pre32_compatible
3.6.6 Controlling Transaction Replay
RTR has implemented the capability of controlling transaction replay in cases
where a "killer message" happens during a transaction replay preventing recovery
from continuing normally. A "killer message" presents a situation where server
availability is lost because of the presence of a message capable of causing
repeated server application failure during recovery. This is typically the result
of an improperly handled condition or application programming error within
the server itself. Under such circumstances it may be desirable to sidestep a
particular transaction, maintain server operation, and manually process the
transaction at some later time.
The RTR solution is to establish, for a given partition, the maximum number of
retries for any given transaction presented during recovery. Once this limit has
been exceeded, the offending transaction is removed from the recovery process
and is written to the journal as an exception record. Subsequent processing of
this transaction requires manual intervention by someone qualified to evaluate
and correct the situation in both the application and in RTR. Once the application
status is understood, the
set transaction
command can be used to update the
journal, thus insuring that the final state of any manually transacted exceptions
are accurately reflected in future recovery operations.
The recovery retry count indicates the maximum number of times that a
transaction should be presented for recovery before being written to the journal
as an exception. Once a transaction has been recorded as an exception, it is
no longer considered eligible for recovery and requires manual processing by a
qualified individual.
The recovery retry count is partition-specific, and applies to both local and
shadow recovery operations. The default is no limit on the number of retries,
which permits a killer message to bring down all available servers servicing a
given partition.
The recovery retry count should be set before starting (or restarting) the
application servers so that the limit is established prior to the start of recovery
operations.
3.6.6.1 Command Line Example
RTR> SET PARTITION/RECOVERY_RETRY_COUNT=3 Facility1:Partition1
For more information on the SET PARTITION command see Chapter 6.
3.6.6.2 Programming Information
To set the partition transaction recovery limit, program the
set_qualifier
argument of
rtr_set_info( )
as follows:
rtr_qualifier_value_t set_qualifiers[ 2 ];
rtr_uns_32_t newLimit = . . .;
set_qualifiers[ 0 ].qv_qualifier = rtr_partition_rcvy_retry_count;
set_qualifiers[ 0 ].qv_value = &newLimit;
set_qualifiers[ 1 ].qv_qualifier = rtr_qualifiers_end;
set_qualifiers[ 1 ].qv_value = NULL;
Partition Management 3–9