text: In general, you will not modify a secondary database directly. In order to modify a secondary database, you should modify the primary database and simply allow DB to manage the secondary modifications for you.
  However, as a convenience, you can delete secondary database records directly. Doing so causes the associated primary key/data pair to be deleted. This in turn causes DB to delete all secondary database records that reference the primary record.
  You can use the
  Db::del()
  method to delete a secondary database record.
  Note that if your
  secondary database
  contains duplicate records, then deleting a record from the set of
  duplicates causes all of the duplicates to be deleted as well.
  You can delete a secondary database record using the previously described mechanism only if the primary database is opened for write access.
  For example:
  #include <db_cxx.h> #include <string.h> ... Db my_database(NULL, 0); // Primary Db my_index(NULL, 0); // Secondary // Open the primary my_database.open(NULL, // Transaction pointer "my_db.db", // On-disk file that holds the database. NULL, // Optional logical database name DB_BTREE, // Database access method DB_CREATE, // Open flags 0); // File mode (using defaults) // Setup the secondary to use sorted duplicates. // This is often desireable for secondary databases. my_index.set_flags(DB_DUPSORT); // Open the secondary my_index.open(NULL, // Transaction pointer "my_secondary.db", // On-disk file that holds the database. NULL, // Optional logical database name DB_BTREE, // Database access method DB_CREATE, // Open flags. 0); // File mode (using defaults) // Now associate the primary and the secondary my_database.associate(NULL, // Txn id &my_index, // Associated secondary database get_sales_rep, // Callback used for key extraction. 0); // Flags // Name to delete char *search_name = "John Doe"; // Get a search key Dbt key(search_name, strlen(search_name) + 1); // Now delete the secondary record. This causes the associated primary // record to be deleted. If any other secondary databases have secondary // records referring to the deleted primary record, then those secondary // records are also deleted. my_index.del(NULL, &key, 0);