IMPAX stores DICOM objects in cache so that they can be displayed, transmitted to other DICOM devices, and archived. Prior to IMPAX 6.5, the cache structure is flat (each cache volume contains one directory) which limits the cache size because once a certain number of objects are in the directory, access to the cache can become very slow. Large sites may resolve this problem by deploying numerous cache volumes, which can be difficult to manage.
As of IMPAX 6.5, a hierarchical cache structure is supported for image and web caches, permitting larger cache volumes. (The old flat cache structure continues to be supported; only new images arriving in the system or existing images retrieved from archive are written to cache using the hierarchical structure.)
 | Note: The default configuration setting for the cache directory structure is YYYYMM, meaning that one additional cache level is created and a new directory is added monthly. |
To configure the hierarchical cache directory structure
Log into the Database Server.
To change the configuration setting, type
UPDATE map_ini SET ini_value = setting WHERE ini_section = 'GENERAL' AND ini_key = 'IMAGE_CACHE_DIRECTORY_STRUCTURE'
or
To add the configuration setting, type
INSERT INTO map_ini (ini_section, ini_key, ini_value) VALUES ('GENERAL', 'IMAGE_CACHE_DIRECTORY_STRUCTURE', 'setting')
where setting must be one of the following formats:
''—(empty single quotes) disables hierarchical cache; flat file system
'YYYYMM'—one additional cache level; a new directory is created monthly
'YYYYMM/DDHH'—two levels of hierarchy; a new directory is created each hour
'YYYYMM/XXXX'—two levels of hierarchy; where XXXX is the first four digits of the hex value of the ordinal
To refresh cached data, type
flush_mem_caches
To exit CLUI, type exit.