The best replacement for rdbms is nosql.

The best alternatives to rdbms are rated as following:
★★★★★  nosql
★★★★  dbms
★★★★  oodbms
★★★  odbms
★★★  ordbms
★★★  non rdbms
★★  hadoop
★★  olap
★  hbase
★  cassandra
★  mpp
★  big data
★  isam
★  mapreduce
★  graph database
  file system
  flat file
  flat files
  orm
  mongodb
  dbms ppt
  oodbmsrdbms

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Speaking about rdbms, one probably shouldn't forget about oodbms.

Other search terms related to rdbms and their ratings are:
★★★★★ oodbms
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