C.5 Disk space requirements when using report cache files

(1) Estimation formula

The report cache files consist of the three types of files listed below. The disk space required for the report cache files is the sum of the sizes of all three types of files.

• Row data file

• Time and position information file

• Row data file pointer lists file

Each time a report is displayed or output while the report cache file function is enabled, a new directory is created under the report cache file storage directory and then the report cache files are stored in that directory.

Note

If multiple reports are displayed concurrently, disk space equivalent to the total size of the report cache files for all the reports is required.

The following shows the formula for estimating the disk space required for report cache files:

C = t × (i × (f + d + 9) + 12)

Legend:

C: Disk space required for report cache files

t: Output data time value^#1

i: Number of record instances

f: Number of fields per record^#2

d: Total length of field data per record (bytes)^{#2, #3}

#1

This value is obtained from the formula (report-interval × display-period) + 1. For example, if the report interval is Hours and the report display period is the past seven days, the output data time value is 24 hours × 7 days + 1 = 169. Note that the report interval available for PD and PL record types is always Minutes.

#2

Include in the estimate the fields that are added automatically based on the report type, as shown below.

Report type	Fields added automatically
Real-time report	Record Time Record-specific ODBC key field (multi-instance records only)
Historical report (single agent)	Date and Time Record-specific ODBC key field (multi-instance records only)
Historical report (multiple agents)	Date and Time Agent Host Agent Instance

#3

For the length of the data in each field, check the field's data type, which is added only when the field is recorded in each record and Store database, as described in the PFM - Agent or PFM - RM manual, and then obtain the corresponding data length from the table shown below.

The length of a field whose data type is char(n) or string(n) is variable. Therefore, use the maximum value for n. For non-ASCII double-byte characters stored in the Store database, each character is saved as three bytes, not two bytes, because these characters are converted to UTF-8 when they are recorded in the report cache files. This means that the formula depends on the lengths of the characters stored in the fields.

Data type	Data length (bytes)
char(n) string(n)	n + 4 (for single-byte characters) (n × 1.5) + 4 (for double-byte characters)
float	4
double	8
short	2
ushort long word	4
ulong	8
time_t timeval utime	8
uchar	4

For a combination report, the disk space required for the report cache files is the sum of the report cache files for all the reports included in the combination report. The following shows the formula for estimating the disk space required for a combination report:

C = C₁ + C₂ + ... + C_R

Legend:

C: Disk space required for the report cache files for a combination report

C₁, C₂, ..., C_R: Disk space required for the report cache files for each report

R: Number of reports included in the combination report

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(2) Example estimate

This example displays a health check agent's PI_HAVL records in a report.

The following are the prerequisites:

• Report type: Historical report (single agent)

• Number of record instances (number of monitored agents): 4

• Display period: Past seven days

• Report interval: Minutes

• Fields to be included in the report: Availability, Total Available Time, and Total Monitoring Time

Prior to the estimate, this example obtains the data length of each field contained in the report. Considering the ODBC key field and the fields that are added automatically based on the report type, the fields included in the report and their data lengths are as follows:

Field	Data type	Data length
Date and Time	time_t	8
Host	string (256)	260
Availability	float	4
Total Available Time	ulong	8
Total Monitoring Time	ulong	8

In this example, the values of the variables shown in C.5(1) Estimation formula are as follows:

• t: 60 × 24 × 7 + 1 = 10,081

• i: 4

• f: 5

• d: 8 + 260 + 4 + 8 + 8 = 288

From the above, the disk space required for the report cache files is as follows:

C = t × (i × (f + d + 9) + 12)

= 10,081 × (4 × (5 + 288 + 9) + 12)

= 10,081 × (1,208 + 12)

= 12,298,820 (bytes)

= approximately 12 (megabytes)

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