The force write ratio (FRCRATIO) parameter specifies the maximum number of records that can be inserted, updated, or deleted before they are forced into auxiliary (permanent) storage.
The force write ratio ensures that all inserted, updated, or deleted records are written into auxiliary storage at least as often as this parameter specifies. In the event of system failure, the only records likely to be lost would be those that were inserted, updated, or deleted since the last force write operation.
The force write ratio is applied to all records inserted, updated, or deleted in the file through the open data path (ODP) to which the force write ratio applies. If two programs are sharing the file, SHARE(*YES), the force write ratio is not applied separately to the set of records inserted, updated, or deleted by each program. It is applied to any combination of records (from both programs) that equals the specified force write ratio parameter value. For example, if a force write ratio of 5 was specified for the file, any combination of five records from the two programs (such as four from one program and one from the other) forces the records to be written to auxiliary storage. If two or more programs are using the file through separate ODPs, the insertions, updates, and deletions from each program are accumulated individually for each ODP.
Each database file can have a force write ratio assigned to it. Logical files, which can access data from more than one physical file, can specify a more restrictive force write ratio (a smaller number of records) than that specified for the based-on physical files. However, a logical file cannot specify a less restrictive force write ratio. If a logical file specifies a less restrictive force write ratio than that specified for any of the physical files, the most restrictive force write ratio from the physical files is used for the logical file. For example, if the force write ratios of three physical files are 2, 6, and 8, the force write ratio of a logical file based on these physical files cannot be greater than 2. If no force write ratio is specified for the logical file, 2 is assumed. Thus, each time a program inserts, updates, or deletes two records in the logical file (regardless of which physical files are affected), those records are forced into auxiliary storage.
The FRCRATIO number overrides the SEQONLY number specified. For example, if you specify:
OVRDBF ... SEQONLY(*YES 20) FRCRATIO(5)
The value of 20 is overridden and a buffer of five records is used. When FRCRATIO(1) is used, a buffer still exists, but it contains only a single record.
Access paths associated with the inserted, updated, and deleted records are written to auxiliary storage only when all the records covered by the access path have been written to auxiliary storage. If only one ODP exists for the file, the access path is forced to auxiliary storage whenever a forced write occurs. If two or more ODPs to the file exist, the access path is written to auxiliary storage whenever all the inserted, updated, and deleted records for all the ODPs have been forced.