Pablo Bucich

HUR Replica - Time Drift

Discussion created by Pablo Bucich Employee on Jan 7, 2014
Latest reply on Jan 8, 2014 by Pablo Bucich

Hello

 

        One of our customers has a long distance DR implementation between two VSP, using HUR and FCIP switches. Because regional limitations, links are slow.
        They are replicating an Oracle DB between sites, and the time drift of data at the DR site changes with the workload during the day, from about 1min up to 20min.
        The customer needs, at any given time, to know the DR time drift (stopping the replica and mounting the DR database is the obvious and very expensive solution ...)

 

        CCI commands:

 

        pairdisplay ... -v ctg

 

        or

 

        pairdisplay ... -v jnl

 

        shows the pending Q-Markers, but I couldn't find a relation Q-Marker -> Timestamp exported at CCI commands. Knowing the Q-Count I think is useless, because some data amount has no direct relation with time drift. I also doubt that Q-Count could be related to some fixed time interval.

 

        I started to develop a small program (a horcm_xx helper) to keep track of timestamp at wich each Q-Marker range is generated (asking each X seconds with pairdisplay), so, knowing the last DR Journal Q-Marker applied you can know the data generation time and then the DR time drift.

 

        At this point I'm working in two programs, one to track qmarkers for a given horcm instance and group, and another that runs pairdisplay, search helper time table to find the nearest timestamp and displays an approximate time drift.

 

        Any comments about Q-Marker -> Timestamp relation, CCI APIs, etc are welcomed

 

thank you
regards

Outcomes