While HiRDB operation is underway, database update logs are accumulated in system log files. When all system log files become full, no more database update logs can be output and the operation of HiRDB cannot continue; as a result, HiRDB terminates abnormally. To avoid a service interrupt due to abnormal termination of HiRDB, the HiRDB administrator must constantly monitor the amount of free space available for system log files.

HiRDB provides a facility for this purpose (monitoring the free area for system log files). When this facility is used, HiRDB monitors the percentage of free area in the system log files and issues a warning message or limits database usage according to a usage level specified by the HiRDB administrator. Either of the following levels can be selected for use by this facility:

Level 1

When the percentage of free area available for system log files falls below the warning value, the KFPS01162-W warning message is output.

Level 2

When the percentage of free area available for system log files falls below the warning value, all transactions at the server are forcibly terminated and scheduling of new transactions is suppressed, which reduces the output to the system log files; the KFPS01160-E message is output.

The following table shows the functional differences between levels 1 and 2.

Table 3-10 Functional differences between levels 1 and 2

Functional item	Level 1	Level 2
Monitors percentage of free area for system log files	Yes	Yes
Outputs error or warning message	Yes	Yes
Suppresses scheduling of new transactions	No	Yes
Forcibly terminates all transactions at the server	No	Yes
Acquires synchronization point	No	Yes

The following formula is used by HiRDB to determine the percentage of free area that is available for system log files:

Percentage (%) of free area for system log files =

Free area in system log files (free area in system log files + update log amount) 100%

The free area in system log files is the sum of the available system log output area in the current file and all areas of log files that are in swappable target status. The update log amount is the system log information from a synchronization point to the most recent log block. The following figure illustrates the concept of free area in system log files.

Figure 3-7 Concept of free area in system log files

Explanation

• The lightly shaded area in files is the update log amount.
• The white area in files is the free area.
• The darkly shaded area in files is system logs that cannot be overwritten, and thus are not subject to rollback. Therefore, this area is not included in either the update log volume or the free area in the system log files.

The percentage of free area for system log files at which the function for monitoring the free area for system log files activates (warning value) is the value at which the database can be relied on to be safely recovered from a system failure (value at which no system log file shortage will occur during database recovery). The warning value depends on the type of server. The following table shows the percentage of free area for system log files at which the function for monitoring the free area for system log files activates (warning value).

Table 3-11 Percentage of free area for system log files at which the function for monitoring the free area activates (warning value)

Type of server		Percentage of free area for system log files at which the function for monitoring the free area activates (warning value)
HiRDB single server configuration		67%
HiRDB parallel server configuration	Front-end server	30%
	Dictionary server	67%
	Back-end server