Uninstalling the repositories will not effect your databases, as only the user owning the DDR repository , dbvisit7 (default user),  gets dropped during the uninstall operation. See example below :

./dbv_setup

=========================================================

    Dbvisit Standby Database Technology (7.0.56.15832)

          http://www.dbvisit.com

    Dbvisit Database setup

      Default values will be shown in []

 Options:

      1) New Dbvisit Database setup (combines options 2,3,4)

      1a) New Dbvisit RAC Instance setup (combines options 2,3,4)

      2) New Dbvisit Database configuration (DDC) file setup

      3) New Dbvisit Archive Management Module (AMM) setup

      4) New Dbvisit Database repository (DDR) setup

      5) Manage Dbvisit Database repository (DDR)

      6) Update Dbvisit Database configuration (DDC) file

      7) Create Standby Database (and template)

      8) Synchronize Standby Database

      9) Uninstall Dbvisit Database repository (DDR)

      E) Exit

=========================================================

Please enter choice : 9

------------------------------------------------------------------------------

=>Uninstalling Dbvisit Database repository (DDR).

Choose database:

The following Oracle database(s) have a Dbvisit Database configuration (DDC)

file on this server:

    DDC

    ===

1)   testdb8

2)   Return to menu

Please enter choice : 1

Is this correct? <Yes/No> [Yes]:

Database testdb8 is up.

Do you want to drop the existing Dbvisit Database repository (DDR) and all of

its contents in database testdb8? Yes or cancel the uninstall? <Yes/Cancel>

[Cancel]: yes

Are you sure? <Yes/No> [Yes]:

Dropping user dbvisit7... this may take a while

User dbvisit7 dropped.

Please press <Enter> to continue…