For background on the differences between the integration engines, please see the following KB articles:
To identify which integration engine you are using, run one of the following commands:
p4 configure show
p4 -ztag info
If neither of the above commands displays the dm.integ.engine variable in the output, then you are using the initial 2011.1 release where the generation 3 engine was set as the default.
To use the generation 2 integration algorithm with a 2011.1+ server, run:
p4 configure set dm.integ.engine=2
To use the generation 3 integration algorithm with a 2011.1+ server, run:
p4 configure set dm.integ.engine=3
When using the generation 2 engine, the server integration engine functions as it has in 2010.2 and earlier versions of p4d (going back to 2004.2). When using dm.integ.engine=2, however, most features of the generation 3 engine are disabled. Those newer features are detailed below.
In the generation 3 engine, the following functionality was introduced:
Resolving "move" actions
Files that have previously been "moved" within the source and/or target branch will be paired up if there was common integration history prior to the move. When the range of source changes to be merged includes "move" actions, a special resolve will be scheduled to accept, ignore, or merge the move action.
Resolving file type and attribute changes
When the range of source changes to be merged includes filetype or attribute changes, a special resolve will be scheduled to accept, ignore, or merge the change. (This eliminates the need to use the -t flag to ensure that filetype changes are propagated.)
Multiple resolves around previous integrations
The new -Rs flag forces multiple resolves to be scheduled per source file when there is a non-contiguous set of unintegrated changes. This prevents previously "cherry-picked" changes from being re-integrated, at the cost of requiring additional merge steps during "p4 resolve".
Modified base selection
The generation 3 integration engine examines the detailed integration history of the source and target files and picks a base with the greatest number of changes in common with the source and target files. The generation 3 integration engine picks a superior base in many complicated scenarios compared to the generation 2 engine. For the best integration performance it's a good idea to keep your server current with the latest release.
Reasons for Changing Integration Engines
Since the generation 2 algorithm has been in place since 2004, many sites have very tightly coupled their integration processes with the behavior of the generation 2 algorithm. If this is the case, or the results from the integration 3 engine are unexpected or problematic, the dm.integ.engine configurable can be set to 2, if it is not already in effect.
For complicated integration histories, users will enjoy the additional benefits of the generation 3 base selection algorithm, handling delete resolves, merging content across moved files, and resolving file type and attribute changes.
The generation 3 engine is always in use for streams-enabled depots, even when the server is configured to use the generation 2 engine.