DP 8 has a 'autovacuum' feature which makes it un-necessary to do the 'writedb/readdb' any more. As a matter of fact, I looked at the command-line arguments for 'omnidbutil' and neither 'writedb' nor 'readdb' are options any more
-autovacuum
Recovers or reuses disk space occupied by updated or deleted rows. The vacuum operation
(periodic maintenance) is done automatically.
There are a number of options for this that I am not going to post here, but you can read in the CLI (Command Line Interpreter) guide