Daylight Administration - Cache Options

Databases can be configured for caching in several ways to improve their performance. Caching can result in the ThorServer to "holding" some or all of a database in memory for fast access, and supplements the operating system file caching capabilities. Caching is using RAM instead of disk to improve speed and efficiency. Caching may be specified by the configuration of a database, or initiated by client request if allowed by configuration. Caching configuration specifications are normally made by thormake, thorchange, or sthorman.

The following is a description of caching options:

-CACHE_WHEN NEVER

Disable caching; all data remain in the disk files. Ignore caching requests from Thor clients.

-CACHE_WHEN OK

Cache if, when, and as specified by a Thor client. (Synonymous with "ON_REQUEST".)

-CACHE_WHEN ALWAYS

-CACHE_LEVEL WRITETHRU

Read hashtable from RAM, write to disk (and RAM).

-CACHE_LEVEL READWRITE

Read and write hashtable in RAM. Disk synced when necessary.

-CACHE_LEVEL WRITETHRU_ALL

Read entire database from RAM, write to disk (and RAM)

-CACHE_LEVEL READWRITE_ALL

Read and write entire database in RAM. Disk synced when necessary.

Note: The option CACHE_LEVEL is ignored unless CACHE_WHEN is ALWAYS.

The corresponding entries in the my_database.THOR are:

cache level:
cache level: NEVER
cache level: ON_REQUEST
cache level: ALWAYS WRITETHRU
cache level: ALWAYS READWRITE
cache level: ALWAYS WRITETHRU_ALL
cache level: ALWAYS READWRITE_ALL

Both primary and cross-referenced data are cached by default. However, we can select either primary and cross-referenced data are caching. The options for specifying one or the other are:

-CACHE_WHAT DATA

cache data only

-CACHE_WHAT XREFS

cache cross-references only

The corresponding entries in the my_database.THOR are:

cache level: ALWAYS WRITETHRU DATA_ONLY
cache level: ALWAYS READWRITE DATA_ONLY
cache level: ALWAYS WRITETHRU_ALL DATA_ONLY
cache level: ALWAYS READWRITE_ALL DATA_ONLY
cache level: ALWAYS WRITETHRU XREFS_ONLY
cache level: ALWAYS READWRITE XREFS_ONLY
cache level: ALWAYS WRITETHRU_ALL XREFS_ONLY
cache level: ALWAYS READWRITE_ALL XREFS_ONLY

Note: Caching the indirect database instead of the "regular" database can result in a great performance improvement. This is especially true for databases with a large number of indirect references per TDT.