Oracle ASM Requirement

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    Is ASM required for doing captures with Oracle? If not, what are best practices for doing captures without ASM?


    Hi there!

    HVR supports capturing changes from Oracle even if the datafiles are automatically managed by ASM or not. If your Oracle uses ASM to manage the redo logs, you will then need to provide access information for the ASM user.  HVR then uses the ASM API to capture the chanages. If ASM is not used, then HVR will perform a direct read against the redo log files at the filesystem. It has been observed that that speed of capturing changes from direct disk reads performs faster than when the database uses ASM.

    I hope that helps. So yes, HVR support capturing from Oracle with or without ASM. We also support capturing from the primary database or from a standby instance.

    Good luck with your replication projects.


    Glenn G.


    Yes, the database does use ASM. So, my next question is, is there a way to capture changes without using the redo logs, or using the redo logs without ASM?


    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, 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/[email protected] 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.






    We’re on Oracle 12 and logs are on ASM. So, if I understand correctly, we need an Oracle account that has SYSASM privileges. The DBA team has concerns about giving an account this much access, especially in a shared ASM environment. Looking at the documentation they said they would have been more comfortable with the old way of only having to grant select any transaction. Is there any way to have ASM access that is more restricted? Thanks.

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