UseLastModified

Enable last-modified response headers. Enables or disables inclusion of the Last-Modified header in cacheable HTTP responses emitted by Image Serving.

The server uses the most recent catalog::TimeStamp value of all catalogs/catalog records involved in a response as the Last-Modified header value.

Should be enabled only if a distributed caching network or other caching system is used which does not support etag headers.

NOTE

Care must be taken when using Last-Modified headers in a load-balanced environment involving multiple Image Serving hosts. Client caching may be defeated and server load increase if for some reason the servers have different time stamps for the same catalog entries. Such a situation can occur as follows:

Neither catalog::TimeStamp nor attribute::TimeStamp, so that the modification time of the catalog.ini file is used as the default for catalog::TimeStamp.
Instead of sharing the image catalog files by way of a network mount, each server has its own instance of the catalog files on a local file system.
Two or more instances of the same catalog.ini file have different file modification dates, possibly caused by improper copying of the files.