With diskless servers, the cache size is dependent on the presence and size of disk-based tables (D-tables) in the database.
Because a diskless server does not use any disk storage space, all D-tables must be stored in the database cache. The cache size is set with the IndexFile.CacheSize parameter, see IndexFile section.
When calculating the cache size take the following factors into consideration:
▪ If the database on a diskless server contains only disk-based tables (D-tables), the cache size must be at least 20% greater than the maximum file size (the amount of data set with the IndexFile.FileSpec parameter). The 20% buffer is an estimate that can vary depending on the usage of the database. For example:
▪ If the database on a diskless server contains only in-memory tables (M-tables), a database cache is still required to hold the system tables. With no D-tables, the minimum cache size is 1-2 MB. The space that is occupied by the system tables depends on the number and complexity of database objects and whether Advanced Replication is used or not.
▪ The cache size must be less than the physical memory that is available for running the diskless server, see Maximum file size in diskless servers.