Rohit,

Pre-Copy will do just that it will precopy all tracks from your source to target in preparation for you to activate when you take the consistent copy.

Copy will not do the copy in advance, once you activate the tracks will copy from source to target in the background.

No Copy, is like a snap,  you don't end up with a full copy on your target device unless every track changes on your source.

This is documented in the Timefinder Product Guide available on support.emc.com

As for creating BCV,

create dev count= ,   size = 1000 CYL  emulation=FBA,  config=BCV;

you can also create

BCV+TDEV or RDF1-BCV+TDEV

Check out the Managing devices section of the Array Controls guide on Support.emc.com

-precopy option can be used with the create or recreate actions to start copying tracks in the background, before the copy session is activated. When using this option, a point-in-time copy will be established when the session is activated. Once the session is activated, the session changes to Copy mode.

–copy is the TF option by default. When the copy session is activated, data begins background copying so that a full copy of the data will become available on the target device.

-nocopy When activating a copy session in nocopy mode, the default device pair state is CopyOnAccess. This means that after activating the copy session, only those tracks that have been written to the source or written/read from the target will be copied to the target device.

For creating BCV with symconfigure command, you can use config=bcv/BCV+R‑5 or BCV‑R‑5 in command file. See:BCV device creation for example

By default nocopy will copy on access, writes to either source or target, but also on read from target.

There is an environment variable that will control the copy on read.  I'm pretty sure that it is DISABLED by default. AFAIK ENABLING it will set it so it doesn't copy on read from target.

  SYMCLI_CLONE_COPY_ON_WRITE: Changes clone nocopy mode when clone session is

                              activated. ENABLED sets clone nocopy mode to

                              copy_on_write. DISABLED sets clone nocopy mode to

                              copy_on_access.