To distribute the compression work, multiple Curators can run concurrently in IMPAX, contending for PREPARE jobs and storing curated images to the shared web cache or caches. The first Curator started is considered the master Curator, and any additional Curators are considered secondary or slave Curators.
When the master Curator is started, it creates a Curator job queue and starts managing the web cache. The master Curator and secondary Curators check for PREPARE jobs in the Curator job queue, process the images into Mitra wavelet format, and store the images in the web cache. Although the Curator job queue and the web cache are owned by the master Curator, PREPARE jobs are associated with the Curator process that accepts the job.
The DICOM Storage Cache Server (using SPFTP) and DICOM Authenticated Storage Cache Server (using ASPFTP) provide images to the IMPAX Application Server and IMPAX Clients (respectively) and are installed with Curator. Because the master Curator owns the web cache, only it is responsible for servicing requests for wavelet images. The secondary Curator processes only curate images and store them to the web cache. Both master and slave Curators can read and write to the web cache, but to configure the distribution of wavelet images so that all Curators can service requests for images, a load balancer is required.
 | Note: All Curator processes must have unauthenticated access to the shared web cache. If Curator and Network Gateway components are installed together, all caches (image and web) must be shared. |
Autopilot is installed with all Curators, but only the Autopilot running on the master Curator is responsible for managing the web cache. If the master Curator fails or is unavailable for an extended period of time, a secondary Curator can be configured to take the role of the master Curator, taking ownership of the web cache and the Curator job queue.