Designing HiRDB file system areas for RDAREAs

For update processing, character special files are more reliable than regular files. Regular files may become inaccessible if the OS terminates abnormally. Thus, character special files should be used for HiRDB file system areas for user RDAREAs that satisfy the following characteristics:
- User RDAREAs for storing tables that are used primarily for update processing.
- User RDAREAs for storing particularly important data.
Calculate the size of the required HiRDB file system area and create a HiRDB file system area of that size or larger.
HiRDB file system areas for RDAREAs must be created at the server machine where the single server is defined.
For the following RDAREAs, create HiRDB file system areas on the server machine where the single server is defined:
- System RDAREAs
- Data dictionary LOB RDAREAs
- Registry RDAREAs
- Registry LOB RDAREAs
For the following RDAREAs, create HiRDB file system areas on the server machine where the single server is defined:
- User RDAREAs
- User LOB RDAREAs
If the system switchover facility is to be used, the HiRDB file system areas for user RDAREAs should be allocated as character special files.

You should create separate HiRDB file system areas for the following types of RDAREAs:
- System RDAREAs
- Data dictionary LOB RDAREAs
- User RDAREAs
- User LOB RDAREAs
- Registry RDAREAs
- Registry LOB RDAREAs
You should create HiRDB file system areas for system files on hard disks separate from the ones used for HiRDB file system areas for RDAREAs. In this way, you can distribute input/output operations when collecting a synchronization point dump, thereby reducing the amount of time required to collect the synchronization point dump.
If you are not using the prefetch facility, the sequential read speed is faster with regular files than with character special files.
For random one-page reads, processing speed is faster with character special files than with regular files.
For write processing, the speed is faster with character special files than with regular files.
Regular files have a hierarchical structure; therefore, as files become larger, the hierarchical levels increase. When you access such files with many hierarchical levels, the number of input/output operations increases, adversely affecting the access efficiency.

The HiRDB file system areas should be allocated as shown in the following table, so that input/output time can be reduced.

Table 8-1 Allocation of HiRDB file system areas to improve performance

Type of HiRDB file system areas	File to be allocated
HiRDB file system area for system RDAREAs	Character special file
HiRDB file system area for dictionary LOB RDAREAs
HiRDB file system area for user LOB RDAREAs
HiRDB file system area for user RDAREAs that store frequently updated tables or tables primarily subject to retrieval of small amounts of data
HiRDB file system area for user RDAREAs that store tables with a large amount of data that are primarily subject to retrieval of all entries or retrieval of large amounts of data by key using the cluster key (but with data that is rarely updated)	Regular file (when not using the prefetch facility) Character special file (when using the prefetch facility)