7.3.12 Operands related to synchronization point dump files

37) pd_spd_dual = Y | N
Specifies whether to use dual synchronization point dump files.
Y: Uses dual synchronization point dump files.
N: Does not use dual synchronization point dump files.
Advantage
When dual synchronization point dump files are used, HiRDB collects the same synchronization point dump in both dump files A and B. Even when an error occurs in one of the files when the collected synchronization point dump is being loaded, the synchronization point dump can be loaded from the other file, thus improving system reliability.
Relationship to other operands
To use dual synchronization point dump files, specify the name of synchronization point dump file B in the pdlogadpf operand.
38) pd_spd_assurance_msg = Y | N
Specifies whether or not the KFPS02183-I message is to be output when a synchronization point dump is completed.
Y: Output the message.
N: Do not output the message.
39) pd_spd_assurance_count = number-of-guaranteed-valid-generations
[Figure]<unsigned integer>((1-2))
Specifies the range of system log files to be saved during HiRDB operation as a protection against events such as a synchronization point dump file input error during system recovery. What is specified here is a number of synchronization point dump file generations; the specified value is referred to as the number of guaranteed-valid generations. The number of past generations of synchronization point dump files specified here are overwrite disabled.
Advantage
When 2 is specified as the number of guaranteed-valid generations and an error occurs in the most recent synchronization point dump file generation, the system can be recovered using the preceding synchronization point dump file generation, resulting in higher reliability.
Specification guideline
  • To improve reliability, 2 should be specified for the number of guaranteed valid generations. However, the number of overwrite disabled synchronization point dump files increases (to two).
  • If reliability has been improved with the use of dual synchronization point dump files, Hitachi recommends that you omit this operand or specify 1 for it.
Notes
  • The minimum number of synchronization point dump files needed is number-of-guaranteed-valid-generations + 1.
  • Specifying 2 increases the number of overwrite disabled synchronization point dump files. Moreover, the system log files that correspond to the overwrite disabled synchronization point dump files are also overwrite disabled. Consequently, specifying 2 for the number of guaranteed valid generations increases the number of overwrite disabled system log files. As a result, a shortage may occur in the number of system log files that can be swapped in. To prevent this, it may be necessary to reevaluate the system log file capacity.
40) pd_spd_reduced_mode = reduced-mode-operation-option
[Figure]<unsigned integer>((0-2))
Specifies whether or not the reduced mode operation for synchronization point dump files is to be used.
Reduced mode operation is a facility for continuing processing if at least two synchronization point dump files can be used, even if an event such as a file error during HiRDB operation or restart reduces the number of synchronization point dump files to or below the number of required files (number of guaranteed valid generations* + 1).
* Value specified for the pd_spd_assurance_count operand.
0: Do not use the reduced mode operation.
1: Use the reduced mode operation.
2: Use the reduced mode operation and issue a warning message whenever a synchronization point dump is being acquired during the reduced mode operation.
41) pd_spd_reserved_file_auto_open = Y | N
Specifies whether or not a synchronization point dump file is to be opened automatically. When Y is specified and an error in a synchronization point dump file reduces the number of synchronization point dump files to the number of files necessary for operation (number of guaranteed valid generations* + 1), HiRDB opens a reserved file (if one is available), makes it overwritable, and continues processing. This is called automatic opening of synchronization point dump file.
* Value specified for the pd_spd_assurance_count operand.
Y:
Open a synchronization point dump file automatically. A reserved file is opened when the number of files falls below the number necessary for operation (number of guaranteed valid generations + 1).
N:
Do not open a synchronization point dump file. No reserved file is opened, even though the number of files falls below the number necessary for operation (number of guaranteed valid generations + 1).
Relationship to other operands
This operand has a higher priority than the pd_spd_reduced_mode operand.
42) pd_spd_max_data_size = synchronization-point-dump-file-buffer-size
[Figure]<unsigned integer>((32000-4000000)) (Bytes)
Specifies in bytes the size of the buffer (shared memory) to be used for synchronization point dump file input/output operations.
The value specified here affects the number of synchronization point dump file input/output operations.
Specification guidelines
  • Normally, this operand need not be specified.
  • When the value of this operand is increased, the number of synchronization point dump file input/output operations is reduced.
43) pd_log_sdinterval = system-log-output-volume[,interval]
Specifies the collection interval for synchronization point dumps. The following should be taken into consideration in specifying this operand:
  • Volume of system log information output since the previous synchronization point
  • Amount of time that has elapsed since the previous synchronization point
system-log-output-volume: [Figure]<unsigned integer>((100-100000)) (Number of log blocks)
Specifies an interval between synchronization point dumps in terms of the number of blocks of log information. A synchronization point dump is collected each time system log information equivalent to the number of log blocks specified here has been output.
interval: [Figure]<unsigned integer>((0 or 10-1440)) (Minutes)
Specifies a synchronization point dump collection interval in terms of number of minutes between synchronization point dumps.
  • When 0 is specified for the interval, HiRDB does not use a time interval for collecting synchronization point dumps.
  • If no transactions execute during an interval, no synchronization point dump is collected even though the amount of the time specified here has elapsed.
Specification guidelines
  • This operand need not be specified if no specific amount of time is specified for restarting HiRDB.
  • The value specified for this operand affects the amount of time required to restart HiRDB.
  • Specifying a small value for this operand reduces the amount of time required for database recovery during a HiRDB restart. However, because the frequency of synchronization point dumps increases, online performance may deteriorate in some cases.
    Conversely, specifying a large value for this operand increases the amount of time required for database recovery during a HiRDB restart. However, because the frequency of synchronization point dumps decreases, online performance may improve in some cases.
Tuning the specified value
The synchronization point dump collection interval can be checked with the statistics analysis utility; the relevant information is shown under SYNC POINT GET INTERVAL in the statistical information related to system operation. The average SYNC POINT GET INTERVAL value should be used. If the synchronization point dump collection interval is determined to be too long, the specification value should be decreased; conversely, if it is determined to be too short, the specification value should be increased.
Note
The synchronization point dump collection interval is determined on the basis of the volume of system log information that is output. Therefore, committing data from memory to a database takes a long time during intervals that have few updating transactions. If an error occurs at such a time, it will take longer to recover the transactions that were generated during that period. If this is a possibility, the synchronization point dump collection interval should be set by also using the interval value.