MSI Custom Action Type Flags

Value added to Type	Effect
0	Synchronous execution. Fails if exit code is not zero., Always executed. Immediate execution.
+64	Synchronous execution. Exit code is ignored
+128	Asynchronous execution. Fails if exit code is not zero.
+192	Asynchronous execution. Exit code is ignored
+256	Execute once. If the action is in both the UI and Execute sequence tables, it is executed only in the UI sequence table if the user interface is used, and it is executed only in the Execute sequence table if the user interface is not used.
+512	Execute once per process. If the action is in both the UI and Execute sequence tables, and both tables are read by the same process, it is executed only in the UI sequence table if the user interface is used, and only in the Execute sequence table if the user interface is not used
+768	Execute only on client after UI sequence. This custom action is in the Execute sequence table, but it should not be run if the user interface is suppressed.
+1024	Deferred execution custom action
+1280	Rollback custom action
+1536	Commit custom action
+3072	Deferred custom action run in the system process.