This section describes the design considerations for synchronization point dump files.
As a safeguard against the possibility of hard disk failures, the synchronization point dump files should be created on separate hard disks. If this is not possible, adjacent generations of files should be created on separate hard disks, as shown in the example in Figure 10-5.
Figure 10-5 Example of creating adjacent generations on separate hard disks (HiRDB/Parallel Server)
When the synchronization point dump file is duplexed, HiRDB collects the same synchronization point dump on both system A and system B. This increases system reliability, because when a collected synchronization point dump is read and there is an abnormality in the file, the synchronization point dump can still be read from the other file. Duplexing also enables the number of guaranteed-valid generations to be set to one generation, yet reliability is not compromised and the number of synchronization point dump files in overwrite disabled status is reduced.
Specify the following operands in the server definition to enable duplexing of synchronization point dump files:
Each synchronization point dump acquired by HiRDB is stored in a separate synchronization point dump file. HiRDB uses the generation concept to manage synchronization point dump files. The HiRDB administrator specifies the number of generations of synchronization point dump files, and the corresponding system log files, that are to be placed in overwrite-disabled status. This concept is called the number of guaranteed-valid generations for synchronization point dump files, and it is illustrated in Figure 10-6.
Figure 10-6 Number of guaranteed-valid generations for synchronization point dump file (HiRDB/Parallel Server)
The required number of synchronization point dump files is the number of guaranteed-valid generations + 1. Specify the number of guaranteed-valid generations for synchronization point dump files in the pd_spd_assurance_count operand in the server definition.
If synchronization point dump files are to be duplexed, it is recommended that only one guaranteed-valid generation be required. If duplexing is not to be used, two generations are recommended.
If the number of synchronization point dump files available for use is reduced to the number of guaranteed-valid generations + 1 because of errors in synchronization point dump files, processing can continue with a minimum of two files. This is called the reduced mode operation for synchronization point dump files.
To perform reduced mode operation for synchronization point dump files, specify the pd_spd_reduced_mode operand in the server definition.
When the number of synchronization point dump files available for use is reduced to the number of guaranteed-valid generations + 1 because of errors in synchronization point dump files, processing can continue by opening a reserved file and placing it in overwrite-enabled status (assuming that such a reserved file is available). This is called automatic opening of synchronization point dump files.
To perform automatic opening of synchronization point dump files, specify the pd_spd_reserved_file_auto_open=Y in the server definition.
The pdlogadfg and pdlogadpf operands are used to define the correspondence between file groups and the created synchronization point dump files.
If only the pdlogadfg operand is specified, synchronization point dump files can be added during HiRDB operation.