Generally, IBM delivers three types of IBM Spectrum LSF patches, Interim Fixes, Fix Packs and Service Packs.
Interim Fix - a fix that contains one or more product defects/APARs. This is the most common patch that IBM delivers. When a client reports an issue that is confirmed as a product defect, technical support delivers this type of patch to the client to fix the product defect.
Fix Pack - a cumulative collection of all fixes since the last release. Usually IBM releases new Fix Packs every 4 months.
Service Pack - a new significant feature release or a new platform supported by LSF.