25.13.6 Handling of statistics log files

When the standby system switchover facility is used, the statistics log files consist of the two files pdstj1 and pdstj2. These files are created automatically for both the primary system and the secondary system, so the HiRDB administrator must prepare a total of four files. Statistics log files cannot be shared between the primary system and the secondary system.

When the standby-less system switchover (1:1) facility or the standby-less system switchover (effects distributed) facility is used, the statistics log files consist of the two files pdstj1 and pdstj2. These files are created as a set for the primary HiRDB system. Because the accepting unit's statistics log files are shared at the switching destination, no files are created for the secondary system. The HiRDB administrator must prepare files for the regular unit and for the accepting unit.

Organization of this subsection
(1) Creating unload statistics log files
(2) Process for collecting statistical information after a system switchover
(3) Executing the statistics analysis utility

(1) Creating unload statistics log files

(a) When using the standby system switchover facility

Because statistics log files are distributed to each server machine when system switchover occurs, create unload statistics log files on a specific server machine. Hitachi recommends creating unload statistics log files in the following cases:

Figure 25-70 shows examples of unload statistics log files created when a system switchover facility is used.

Figure 25-70 Examples of unload statistics log files created when a system switchover facility is used (Part 1)

[Figure]

Hint
Each server machine has a statistics log file with the same name. Be sure to create your unload statistics log file with a different name. Even when using the shell script provided by HiRDB (pdstjacm), modify the shell script so each unload statistics log file has a different name.
(b) Standby-less system switchover (1:1) facility or standby-less system switchover (effects distributed) facility

When system switchover occurs, the statistics log files to be used by the switching-destination host are the files being used by the accepting unit at the switching destination. Because statistics log output destination files are distributed to each host, unload statistics log files must be created on a specific server machine.

You should create unload statistics log files at the following times:

Figure 25-71 shows examples of unload statistics log files created when a system switchover facility is used.

Figure 25-71 Examples of unload statistics log files created when a system switchover facility is used (Part 2)

[Figure]

Hint
Because statistics log files have identical names on all server machines, do not use the same names when you create the unload statistics log files. Also, when using a shell script (pdstjacm) provided by HiRDB, change the shell script so that the same name is not used.
When system switchover occurs, statistics log files are handled by the switching-destination host.

(2) Process for collecting statistical information after a system switchover

(a) Standby system switchover facility

After system switchover occurs, the following operands specify whether or not statistical information is to be collected by the HiRDB on the switchover destination system:

If Y is specified in the pd_statistics operand or the pdstbegin operand is specified, statistical information is collected immediately after system switchover occurs.

If system switchover occurs when the pdstbegin command is being used to start collecting statistical information, HiRDB on the switchover destination system cannot collect statistical information. To collect statistical information in this situation, you must use HiRDB on the switchover destination system to execute the pdstbegin command.

Also, HiRDB on the switchover destination system determines whether the pdstj1 or the pdstj2 statistics log file will be used. The procedure for determining which statistics log file will be used is the same as when the system switchover facility is not used.

(b) Standby-less system switchover (1:1) facility

The process for collecting statistical information when in alternating status is explained below. The collection status of statistical information on the alternate BES unit determines whether or not collection of statistical information is necessary on a normal BES unit in alternating status. The same types of statistical information are collected on the normal BES unit and on the alternate BES unit. Figure 25-72 shows the process of collecting statistical information in the alternating status.

Figure 25-72 Process of collecting statistical information in alternating status

[Figure]

Explanation
The process of collecting statistical information for BES1 and BES2 when in alternating status is explained below:
  • BES1: Collects the same buf and dfw as the alternate BES unit (BES3).
  • BES2: Collects the same sys as the alternate BES unit (BES4).
The process for BES3 and BES4 is the same.
In addition to the statistical information for BES3 and BES4, the statistical information for BES1 and BES2 is output to the statistics log file in the alternate BES unit (UNT2).
Remarks
The collection status of statistical information for a normal BES unit and an alternate BES unit in alternating status and the types of statistical information collected are the same. Figure 25-73 is used as an example in the following explanations.
  • When the pdstend command stops collection of statistical information for BES3, the statistical information for BES1 can no longer be collected. Similarly, when the pdstend command stops collection of statistical information for BES1, the statistical information for BES3 can no longer be collected.
  • When the pdstbegin or pdstend command changes the types of statistical information collected for BES3, the types of statistical information for BES1 are also changed. Similarly, when the pdstbegin or pdstend command changes the types of statistical information collected for BES3, the types of collected information acquired for BES3 are also changed.
When switching a system back
When switching a system back (returning from alternating status to normal status), the operands listed below specify whether or not statistical information of the normal BES unit is to be collected and the types of statistical information to collect:
  • pd_statistics
  • pdstbegin
Therefore, you must execute the pdstbegin command again when changing whether or not to acquire statistical information or when changing the types of information to be collected.
(c) Standby-less system switchover (effects distributed) facility

When system switchover occurs, the statistics log collection status that existed immediately before system switchover is inherited. That is, if statistics logs were being collected before the system switchover, statistics logs will continue to be collected at the switched server after system switchover, regardless of the value specified in the pd_statistics operand of the system common definition. In this case, the statistics log files are shared with the accepting unit at the switching destination. If statistics logs were not being collected immediately before system switchover, no statistics logs will be collected after system switchover; you can begin collecting statistics logs by entering the pdstbegin command after switchover.

Table 25-47 shows when statistics logs are collected when the standby-less system switchover (effects distributed) facility is used.

Table 25-47 Statistics log collection when the standby-less system switchover (effects distributed) facility is used

Unit typeBeing collectedAccepting unit
Regular unitWas being collected.Collects.
Was not being collected.Does not collect.

Figure 25-73 shows an example of statistics log collection after system switchover when the standby-less system switchover (effects distributed) facility is used.

Figure 25-73 Example of statistics log collection after system switchover when the standby-less system switchover (effects distributed) facility is used

[Figure]

(3) Executing the statistics analysis utility

(a) Standby system switchover facility

The statistics analysis utility is executed using the created unload statistics log files as the input information. If system switchover occurs due to an error, the statistics log information immediately prior to system switchover is not acquired correctly in the file. For this reason, the execution results of the statistics analysis utility may not be accurate when used for tuning, etc.

(b) Standby-less system switchover (1:1) facility or standby-less system switchover (effects distributed) facility

The statistics analysis utility is executed using the unload statistics log files created at the regular unit and the accepting unit as the input information. To manually copy the files that existed prior to system switchover you must use, for example, an OS command. The statistics information on the server that has been switched is processed as information on a server belonging to the accepting unit.

If system switchover occurs because of an error, the statistics log information immediately prior to system switchover is not acquired correctly in the file. For this reason, the execution results of the statistics analysis utility may not be accurate when used for tuning, etc.