4.2.13 Operands related to system log files

43) pd_log_dual = Y | N
Specifies whether dual system log files are to be used.
Y: Use dual system log files.
N: Do not use dual system log files.
Advantages
When dual system log files are used, HiRDB collects the same system log information in both files, which are called File A and File B. If a failure occurs in one of the files while the collected system log file is being loaded, the file can be loaded from the other file, resulting in higher system reliability.
Relationship to other operands
When use of dual system log files is specified, the name of the File B system log file must be specified with the pdlogadpf operand in each server definition.
44) pd_log_dual_write_method = serial | parallel
This operand is applicable only to the AIX and Linux (Red Hat Enterprise Linux ES 4 (AMD64 & Intel EM64T) or later or Red Hat Enterprise Linux AS 4 (AMD64 & Intel EM64T) or later) editions of HiRDB.
This operand specifies whether to use the facility for parallel output of system logs. For details about this facility, see the HiRDB Version 9 Installation and Design Guide.
serial: The facility for parallel output of system logs is not used.
parallel: The facility for parallel output of system logs is used.
When parallel is specified in this operand, HiRDB uses the aio library (for AIX, the Asynchronous I/O Subsystem; for Linux, libaio) to execute parallel output to the system log files.
Conditions
All the following conditions must be satisfied before parallel can be specified in this operand:
  • An aio library has been imported and required setup has been performed
  • pd_log_dual = Y
  • The system log files are located in character special files.
If either of these conditions is not satisfied, the facility for parallel output of system logs is not used regardless of the value specified for this operand.
45) pd_log_remain_space_check = warn | safe
Specifies the processing to be performed by HiRDB when the available space in the system log file falls below the warning level. This is called the facility for monitoring the free area for the system log file. For details about this facility, see the HiRDB Version 9 System Operation Guide.
warn:
When the available space in the system log file falls below the warning level, the KFPS01162-W message is output.
safe:
When the available space in the system log file falls below the warning level, scheduling of new transactions is suppressed, all transactions inside the server are forcibly terminated, and the KFPS01160-E message is output.
Specification guideline
We recommend that you specify safe because it can reduce the probability of abnormal termination of units due to system log file space shortage. However, when safe is specified, all transactions inside the server are forcibly terminated when a shortage occurs in the available space in the system log file. Therefore, the design of the system log file requires more accuracy. For details about system log file design, see the HiRDB Version 9 Installation and Design Guide.
46) pd_log_auto_unload_restart = Y | N
Specifies whether the automatic log unloading facility is to be restarted when the system log files are swapped following the issuance of a message indicating that the automatic log unloading facility stopped due to an error (message KFPS01150-E).
Y: Restart the automatic log unloading facility.
N: Do not restart the automatic log unloading facility.
Condition
The following two conditions must be satisfied:
  • Y is specified in the pd_log_unload_check operand or this operand is omitted.
  • The pd_log_auto_unload_path operand is specified.
Advantages
  • If Y is specified in this operand and a shortage of disk capacity occurs due to an increase in the number of work files, or because the unload processing fails due to a temporary error such as a process creation error, HiRDB automatically restarts the unloading of system logs the next time the system log files are swapped.
  • If N is specified in this operand and the unload log files are set to be saved while the automatic log unloading facility is stopped due to an error, you can prevent the unload log files from being saved before the pdlogatul -t command is executed.
Specification guidelines
Normally, specify Y or omit this operand.
Specify N if you have already set HiRDB to monitor the automatic log unloading facility termination message (KFPS01150-E message) and restart the facility with the pdlogatul -b command.
47) pd_log_singleoperation = Y | N
This operand is applicable when dual system log files are used; it need not be specified when dual system log files are not used.
Specifies whether the single-operation mode is to be used for the system log files. Even if an error occurs in a system log file, making no dual system log files available, HiRDB (or a unit for a HiRDB parallel server configuration) can continue processing using the remaining single normal system log file without being abnormally terminated. This is called single operation of the system log files.
The mode in which continuation of processing is permitted only with both system log files available (normal operation mode) is called double operation of the system log files.
Y: Use single operation of the system log files.
N: Do not use single operation of the system log files. Both system log files must always be used.
Condition
Y must be specified in the pd_log_dual operand.
48) pd_log_rerun_reserved_file_open = Y | N
Specifies whether a system log file is to be opened automatically.
If no system log file that can be overwritten is available during a HiRDB (or unit) restart, HiRDB opens a reserved file (if one is available), makes it overwritable, and continues processing. This is called automatic opening of system log file.
A reserved file is used in the following cases:
  • Between the time of a restart and the time when the first synchronization point dump is collected
  • When none of the opened file groups can be overwritten
Y: Open a system log file automatically (open and use a reserved file).
N: Do not open a system log file automatically (do not use a reserved file).
Advantages
When Y is specified, the unit can be restarted as long as a reserved file is available, even though no file that can be swapped in is available during the unit restart.
However, if a file that is in unload wait status is available, the unit is stopped; once that file has been unloaded, the unit can be restarted.
49) pd_log_rerun_swap = Y | N
Specifies whether the system log files are to be swapped during a HiRDB (or unit) restart.
Y: Swap the system log files.
N: Do not swap the system log files.
Advantage
When Y is specified, there can be a physical separation between the system log files used before and after a restart. Therefore, the system log file that was being used before the restart can be reused during server operation.
50) pd_log_swap_timeout = wait-time-for-completion-of-system-log-file-swapping
~<unsigned integer>((1-32580))<<180>> (seconds)
Specifies in seconds the wait time during which swapping of system log files must be completed. If a swap of system log files is not completed within the specified amount of time, the unit terminates abnormally.
Specification guidelines
Normally, there is no need to specify this operand. If it takes a long time to swap system log files for a reason such as poor machine performance, you can specify this operand with a value that is greater than the default value. To detect errors or delays quickly during system log file swapping so that the unit can be terminated (such as because of a disk failure), reduce the value of this operand.
51) pd_log_unload_check = Y | N
Specifies whether HiRDB is to check the unload status of system log files.
Y:
Check the unload status (normal operation).
N:
Do not check the unload status. A system log file is placed in swappable status, regardless of its unload status, when both of the following conditions are satisfied:
  • It is in overwritable status
  • It is in extraction completed status (HiRDB Datareplicator)
  • Overwriting permitted status for online reorganization (HiRDB Staticizer Option)
In such a case, the system log file operation method is to release checking of unload status. For details about this operation method, see the HiRDB Version 9 System Operation Guide.
Advantages
Specifying N provides the following advantages:
  • Operations are simplified because the system log file unload operation is eliminated.
  • It is not necessary to provide files for storing unload files.
Specification guideline
Specify N if the system log file will not be needed for database recovery (in other words, if recovery from a backup collection point will be sufficient).
Notes
The following points apply when N is specified:
  • Database can be recovered only if backups have been made.
  • If this option is specified when the system log file is required for database recovery, it will not be possible to recover the database.
52) pd_log_write_buff_count = log-output-buffer-sectors-count
~<unsigned integer>((10-65000))<<10>>
Specifies the number of buffer sectors to be used for system log output.
Tuning the specified value
Specify 10 (the default) for this operand initially. Thereafter, use a statistics analysis utility to obtain statistical information related to system operation to check the number of waits caused by a shortage of current buffer space (# OF WAIT THREAD). If the number of waits is high, specify a larger value to improve throughput.
Notes
If a small value is specified in this operand and the number of transactions is high, multiple transactions might be waiting for system log output, lowering system performance.
Relationship to other operands
  • Use this operand and the pd_log_max_data_size operand to determine the number of log output buffer sectors.
53) pd_log_auto_expand_size = extension-amount-per-system-log-file-extension-trigger[,extension-limit]
~<unsigned integer>((0-104857600))<<0,0>>(records)
Specify this operand when the system log file automatic extension facility is used.
Specifies the number of records to be added to the system log file for each extension trigger and an upper limit for extending file size.
If the amount to be added per trigger is omitted or 0 is specified, the system log file will not be extended automatically. If the extension limit is omitted or 0 is specified, the system log file might be extended until either the disk on which the file system area is located becomes full or the system log file capacity reaches its upper limit. When a value is specified for the amount to be added per trigger that is larger than the extension limit, the file will be extended up to the extension limit.
For details about the system log file automatic extension facility, see the HiRDB Version 9 System Operation Guide.
Specification guidelines
  • Specify in this operand the amount to be added per trigger based on the number of records specified when the system log file was created with the -n option of the pdloginit command. Determine 10 percent of the average number of records for the system log file for each server and then specify the value for the server that has the largest value.
    [Figure]In the case of a BES that uses the standby-less system switchover (1:1) facility, determine 10 percent of the average value including the system log file of the alternate BES.
    [Figure]In the case of a BES that uses the standby-less system switchover (effects distributed) facility, determine 10 percent of the average value including the system log file of the guest BES.
  • Normally, an extension limit is omitted.
Tuning the specified value
If the system log output volume exceeds the expanded size after automatic extension, the system log file could become full, resulting in a unitdown. In such a case, increase the specified value (number of records to be added per trigger). If extension processing requires so much time that it affects transaction performance, specify a smaller value.