This section describes the formula for estimating the size of an archive journal file.

First, use the following formula to determine the total number of journals to be archived in an archive journal file:

(Total number of journals that are generated by each archive source node during online operation) (unit: bytes)

For details about the total number of journals generated by each archive source node during online operation, see H.2 Estimating the size of a system journal file. Use the estimated size of the system journal file of each node.

The formula for determining the total size of archive journal files that are actually prepared is as follows:

Total number of journals to be archived in archive journal files x 1.2 (safety factor) + 16384 (unit: bytes)

Note, however, that the size of one archive journal file must be larger than the result of the following formula:

(4 + 256 x number of archive source nodes whose data is to be archived in this archive journal file) x 4096 (unit: bytes)

When you use two or more journal files to accommodate the total journal file size calculated above, you do not need to unload journals until online operation ends. If you cannot allocate the calculated total archive journal file size, use 1/n (n > 0) of the total size as your total size and allocate the size among two or more archive journal files. When you do this, one archive journal file is reused for n times until the end of online operation. This means the archive journal file must be unloaded.

To protect against archive journal file failures, allocate reserve archive journal files, if possible. A reserve archive journal file must also have the size shown in the above formula for determining the size of one archive journal file.

Note that one archive journal file makes up a file group. This means that the size of one archive journal file also indicates the size of the file group.

When you duplicate archive journal files by specifying Y in the jnl_dual operand in the archive journal service definition, two files are required for each archive journal file described above, doubling the total size of archive journal files. The paired archive journal files must have the same size. Although OpenTP1 will run if the sizes of the paired archive journal files are different, OpenTP1 uses the smaller of the sizes as the archive journal file size. This wastes space.

If you do not use the parallel access facility of the archive journal file, the size of the file group is the size of the physical file.

When you use the parallel access facility of the archive journal file, you must divide the size of the file group by m^# (m^# > 1), use the divided size as the size of an archive journal file, and prepare archive journal files for at least the minimum number of dispersions for each file group. In this case, the size of the physical file is the size of the element file.

#

m is the value specified in the jnl_max_file_dispersion operand (maximum number of dispersions for enabling parallel access) in the archive journal service definition.