Starting a Postgres slave that is in hotstandy - stuck after start
Although this message could look like an error:


  cp: cannot stat `/usr/local/pgsql/wals/000000010000003B000000BA': No
  such file or directory


it's actually harmless, it's just the way of your restore_command to check for a new WAL file that's not necessarily there yet.
Presumably this command looks like:

cp /usr/local/pgsql/wals/%f "%p"


Should you want to get rid of that message, you could provide a more sophisticated version of the command to silently check for the existence of the file before attempting to copy it.

In the rest of the log output, there is nothing that looks wrong. If it's a hot standby, you should be able to connect to it with psql.