I found the answer, here you go:
Regarding Background Checks: Clearances
Overall, generally,
most applicants are not likely to encounter any more than minimal delays due to background clearances. Some will, most will not.
There are three formal clearances (
background checks) required for grant citizenship applicants.
These are: GCMS; RCMP; and CSIS
They are essentially, respectively:
GCMS: immigration (confirmation of status and admissibility)
RCMP: criminal background, which can be more robust than just the name-record criminal history check, which probably means it can involve queries beyond arrest and disposition records, such as into whether any law enforcement body is conducting an investigation or the individual is a suspect or has known connections to those known to be involved in criminality (the name-record criminal history check is done periodically throughout the process, and is similar to one often conducted during any secondary examination at a POE, and it is mostly a query run against an arrest and dispositions database based on individual's name and date-of-birth)
CSIS: security background (while obviously the scope of this is not public information, it is readily recognized that it at least involves queries into intelligence sourced databases, and other government security databases, which might reveal activity or ties related to organized crime, terrorist organizations, suspect military history)
These clearances are all requested by CPC-Sydney upon the application being placed "in process." The RCMP and CSIS requests are done by referral to, obviously, the RCMP and CSIS. (Thus, the RCMP and CSIS clearances are
not done by CIC, but by referral to the respective government body.)
Previously, for sure, and probably still the case, the fact that clearances are outstanding does not preclude the application moving to the next step in the process
until the test/interview step. It appears clear, though, that any outstanding clearance will delay scheduling the test/interview; note that other participants have recently reported receiving letters specifically indicating their scheduling for the test/interview "may be delayed if security, criminal and immigration background checks are not complete."
In this regard, however, there may be a difference between whether the original clearance, in response to the referral from CPC-Sydney, is complete, in contrast to an expired clearance which is in need of an update.
For sure, clearances will be need to be current, and thus those expired need to be updated, before the oath will be scheduled.
Link:
https://secure.immigration.ca/forum/forum_posts.asp?TID=14710&title=what-does-that-mean-background-check