You asked a couple questions, so let me take one at a time. You asked:
1. is there a way to capture changes without using the redo logs?
Answer: the incremental changes are in the redo logs, so we need to capture the data from the redo logs using one of a few approaches. We can read the files directly (direct read), or we can use a SQL interface, or we access them via the ASM api.
2. can we capture by reading redo without going through the ASM API mechanism?
Answer: Yes, you can configure your Oracle log writer to maintain redo logs both within ASM as well as a second member of redo logs that are accessible directly from disk. This will cause the Oracle log writer to maintain two sets of redo logs, one managed within ASM and one set available on disk.
If your Oracle primary database redo logs are managed by ASM, then we recommend you:
Configuring Oracle ASM
HVR supports log-based capture from Oracle databases whose redo and archive files are located on ASM storage.
There are two ways to configure this:
1. For Oracle 11.2, before Oracle 126.96.36.199, HVR will read the redo and archive files directly through its SQL
2. Define environment variable $HVR_ASM_CONNECT to a username/password pair such as sys/sys. The user needs sufficient privileges on the ASM instance; sysdba for Oracle version 10 and sysasm for Oracle 11+. If the ASM is only reachable through a TNS connection, you can use username/password@TNS as the value of $HVR_ASM_CONNECT. If HVR is not able to get the correct value for the $ORACLE_HOME of the ASM instance (e.g. by looking into /etc/oratab), then that path should be defined with environment variable $HVR_ASM_HOME. These variables should be configured using environment actions on the Oracle location.
I hope this helps.