TF/Clone -precopy and -cycled question

makes sense the -copy answer, that's what i expected but wanted to double check.

i understand why somebody would use -precopy parameter, we do it all the time when we build new pairs but typically we create pairs and let them "drift" until we activate them.  But i am still confused why activating a session that was build with -precopy is not a good idea until it completed one full cycle. When you activate it, it copies track that are still owned to the target ..so who cares that it did not complete one full cycle. Let me give you an example: i have 10TB database, say i build brand new clone relationship using "-precopy -differential", session is created and data is being copied. Let's say 50% into copy process business comes screaming "oh my god, we need this clone right now !".  So i activate the clone and make it available to my DB server ..i know i only have 50% of my data on the clone while the other 50% is still copying in the background ..i am ok with possible increase in response time, they said they wanted it NOW, they got it with slightly degraded performance.  So is it just the performance or 50% of my data would be garbage ?

Thank you for your time, and no ..i am not kidding about crazy business people running into my cube

It's performance.  When you activate a precopy session it effectively becomes a copy session.  So, all the data on the target is good, but you could have an increase in RT if the host accessing the target reads data that has not yet been copied. This is because, in order to provide it to the host, the array has to first copy the data from the source to the target.

That flag is only pertinent when the state of the session is 'PreCopy' and not when the session has been activated and reached a copied state.  At that point, no more data is copying from source to target so the precopy cycle information is no longer relevant.  If you issue a recreate -precopy, the flag will get set when the tracks that were changed since the last recreate have been copied to the target at least once.  The flag will then get cleared again when you activate the session.

fair enough, for some reason i was under impression that if i activate it before it has completed one full cycle i will have data integrity issue on my clone target.

One interesting data point, look at the status of this clone pair, these clones get re-created every day so they have completed hundreds of "full cycles" yet look at the status of "pre-copy operation has completed one cycle". There is a "x" in the CGDP column, any idea why ?

$ symclone -g oracle query 


Device Group (DG) Name: oracle
DG's Type             : REGULAR
DG's Symmetrix ID     : 00000012345 


         Source Device                   Target Device            State     Copy
--------------------------------- ---------------------------- ------------ ----
               Protected Modified                Modified
Logical   Sym  Tracks    Tracks   Logical   Sym  Tracks   CGDP SRC <=> TGT  (%)
--------------------------------- ---------------------------- ------------ ----
DEV001    3945         0        0 TGT001    4717        0 XXX. Copied       100
DEV002    3946         0        0 TGT002    4718        0 XXX. Copied       100
DEV003    23C1         0        0 TGT003    2A92        0 XXX. Copied       100
DEV004    23FD         0        0 TGT004    2ACE        0 XXX. Copied       100
DEV005    2439         0        0 TGT005    4627        0 XXX. Copied       100


Total           -------- --------                --------
  Track(s)             0        0                       0
  MB(s)              0.0      0.0                     0.0

Legend:

(C): X = The background copy setting is active for this pair.
     . = The background copy setting is not active for this pair.
(G): X = The Target device is associated with this group.
     . = The Target device is not associated with this group.
(D): X = The Clone session is a differential copy session.
     . = The Clone session is not a differential copy session.
(P): X = The pre-copy operation has completed one cycle
     . = The pre-copy operation has not completed one cycle

Dynamox,

In that screenshot, you've already activated the sessions so precopy no longer applies. The P flag is only applicable if you're in precopy mode before issuing an activate.

Thanks,

-Sean

Sean and SYMCLIGuy,

Thank you and Thank you  ..so consensus is -cycled is to let users know that all tracks have been copied at least once and user should expect only relatively small amount of data to be copied after activation. It has nothing to do with data integrity ..clones activated before status reaches "pre-copy operation has completed one cycle" will be just as valid if i were to use -copy to create my session ?

Thank you