Thursday, October 19, 2023

Farewell to ClickOps: OCI CLI seamless Data Guard Replication for ExaC@C


Since the very beginning, everyone got introduced to  Cloud services through the console as it’s very quick. But the cloud CLI tooling provides a stronger, yet user-friendly way to automate tasks, often covering features not even available in the console. Moreover, DBAs often assume that the CLI is primarily designed for managing compute-based services, overlooking its potential benefits for their database fleet. In this tutorial, we'll demonstrate how to automate the Data Guard association of your database between two Exadata Cloud at Customer infrastructures in separate regions.
On top of it, I’ll show you where to look and the type of logs that are generated if you need to troubleshoot.


Using the API to Enable Data Guard on ExaC@C

REST API Endpoint
Obviously, Rest APIs provided by the Cloud platform is the core vehicle that allows anything (infrastructure resource, or cloud services) to be created, deleted or managed.
This why the best thing to explore a new feature is to check the REST API Endpoint.
In our case the endpoint is

POST /20160918/databases/{databaseId}/dataGuardAssociations

You can check more details here CreateDataGuardAssociationDetails 

API method for a Data guard association using existing cluster

Below is the configuration details for creating a Data Guard association for a ExaCC Vmcluster database

The attributes are as below

API Attributes
Attributes Required Description Value
creationType Yes Other Options: WithNewDbSystem, ExistingDbSystem ExistingVmCluster
databaseAdminPassword Yes The admin password and the TDE password must be the same.
isActiveDataGuardEnabled No True if active Data Guard is enabled. True
peerDbUniqueName No
  • DB_UNIQUE_NAME of peer DB to be created.
  • Unique across the fleet/tenancy
  • Defaults to
    <db_name>_<3 char>_<region-name>.
    peerSidPrefix No DB SID prefix to be created. unique in the VM cluster
    instance # is auto appended to the SID prefix
    protectionMode Yes MAXIMUM_AVAILABILITY
    transportType Yes SYNC
    peerDbHomeId No Supply this value to create standby DB with an existing DB home
    databaseSoftwareImageId No The database software image OCID

    API request Examples

    Here is a basic API call example for Database system which slightly differs from the Exadata Cloud implantation.


    Response Body

    The response body will contain a single DataGuardAssociation resource.

    Using OCI CLI to Enable Data Guard on ExaCC

    Now that we’ve explored REST API structure, we can move to a practical example using OCI CLI. Both Exada Cloud@Customer (Edge DB service) are located in different regions in Canada in 2 DataCenters.   


    $ oci db data-guard-association create from-existing-vm-cluster [OPTIONS]

    Generate a sample json file to be used with this command option.

    The best way to leverage OCI CLI with a complex structure is to generate a full command JSON construct. 

    # oci db data-guard-association create from-existing-vm-cluster \
    --generate-full-command-json-input > dg_assoc.json
      "databaseAdminPassword": "string",
      "databaseId": "string",
      "databaseSoftwareImageId": "string",
      "peerDbHomeId": "string",
      "peerDbUniqueName": "string",
      "peerSidPrefix": "string",
      "peerVmClusterId": "string",
    ,"transportType": "SYNC|ASYNC|FASTSYNC" }

    Practical Example

    Here we will configure a Data guard setup from an ExaC@C site to another with no existing standby DB home.

    • Below template matches a DG association without a peer Database Home in the standby VM Cluster

    # vi dg_assoc_MYCDB_nodbhome.json

    "databaseAdminPassword": "Mypassxxxx#Z",      
    "databaseId": "",   <--- primary DB
    "databaseSoftwareImageId": null,
    "peerDbHomeId": null,
    "peerDbUniqueName": "MYCDB_Region2",   <--- Standby DB
    "peerSidPrefix": "MYCDB",
    "peerVmClusterId": "", <--- DR cluster
    "protectionMode": "MAXIMUM_PERFORMANCE", "transportType": "ASYNC", "isActiveDataGuardEnabled": true   

    • Now we can run the full command with the adjusted JSON template

    # oci db data-guard-association create from-existing-vm-cluster \
    --from-json file://dg_assoc_MYCDB_nodbhome.json

    Response Body

    Right after the run you’ll have the provisioning starting and the work request assigned

    • You will need the id to check the status (Check for SUCCESS or FAILURE)

    # export workreq_id=ocid1.coreservicesworkrequest.xxxxx
    # oci work-requests work-request get --work-request-id $workreq_id \
    --query data.status


    Automating tasks with CLI provides the advantage of not leaving you in the dark when things go awry. Here are some valuable troubleshooting insights when using OCI CLI

    • The work request status and error detail is easily accessible using get command for troubleshooting 

    • API based operations on existing systems like DB replications, offer comprehensive logs that are invaluable for diagnosing issues inside the target servers (i.e Exadata Cloud VM clusters).

    • Oracle Data Guard association ensures clean rollbacks for quick retries in case of failures - a significant advantage over manual cleanup which we all hated back in on-premises setups.

    Work request

    The very first thing to check is the status of the request and the details of the error in case of failure.

    • Even without a work request ID, the below query allows you to list all previous data guard association jobs

    # oci work-requests work-request list -c $comp_id –-query \
    data[?\"operation-type\"=='Create Data Guard'].\
    --output table

    • The output will look like the below .

    • You want to display details about the error ? Sure there is an oci command for that 

    # oci work-requests work-request-error list --work-request-id $workreq_id –all \
    --query "data[].[code,message]"
    --output table

    • You can see few insights on the stage where your DG association failed for instance

    Logs in your ExaData Cloud@Customer

    When a database related operation is performed on an
    ExaC@C VM , log files from the operation are stored in subdirectories of /var/opt/oracle/log.

    check logs

    Running below find command while your Data guard association is running can help you list the modified logs

    $ find $1 -type f -print0 | xargs -0 stat --format '%Y :%y %n'| sort –nr \
    | cut -d: -f2- | head


    let’s see what logs are created on the primary side

    dg folder

    This will likely contain below files. 

    $ ls /var/opt/oracle/log/GRSP2/dbaasapi/db/dg dbaasapi_SEND_WALLET_*.log dbaasapi_CONFIGURE_PRIMARY_*.log dbaasapi_NEW_DGCONFIG_*.log dbaasapi_VERIFY_DG_PRIMARY_*.log dbaasapi_SEND_WALLET_*.log

    First file created is {log_dir}/<Database_Name>/dbaasapi/db/dg/

    $ tail -f dbaasapi_VERIFY_DG_PRIMARY_2022-05-27_*.log
    Command: timeout 3 bash -c 'cat < /dev/null > /dev/tcp/' Exit: 124 Command has no output
    ERROR: Listener port down/not reachable on node:

    Below excerpt shows the precheck step that failed, which was fixed by running the oci cli command again

    2. PRIMARY_Configure
    After the second run, the prechecks passed, but now there's an issue with the primary configuration (se below).

    Let’s dig a bit deeper , but it seems it’s related to some service not being able to start.

    dgcc folder

    "dgcc" represents the Data Guard Configuration checker, which is responsible for checking the Data Guard status and configurations. Below logs contain information about the activities and status of dgcc on the ExaC@C

    $ ls /var/opt/oracle/log/MYCDB/dgcc dgcc_configure-sql.log dgcc_configure-cmd.log dgcc_configure.log

    dgdeployer folder

    DGdeployer, is the process that performs the DG configuration. The dgdeployer.log file should contain the root cause of a failure to configure the primary database mentioned earlier.

    $ ls /var/opt/oracle/log/MYCDB/dgdeployer

    As displayed here, we can see that the PDB service failed to start

     dgrops folder

    The dgrops  log file contains the output of the dgrops script, which includes the steps performed, the commands executed, and any errors or warnings encountered.
    This log helped identifying the issue which was that the PDB state wasn't saved in the primary CDB.


    On the primary CDB, restart the PDB and save its state and voila.The DG association should now be successful.    

    $ alter pluggable database MYPDB_TEST close instances=all;
    alter pluggable database MYPDB_TEST open instances=all; $ alter pluggable database MYPDB_TEST save state instances=all;


    At this point, there are no troubleshooting steps left. But I though I’d add a list of available logs at the DR site.
     prep folder

    This will store logs about preparation of the standby including creating the DB home based on our previous example

    $ view /var/opt/oracle/log/MYCDB/prep/prep.log

     dg folder

    This folder will include logs pertaining to the standby database creation as shown below

    $ view /var/opt/oracle/log/MYCDB/dbaasapi/db/dg/dbaasapi_CREATE_STANDBY_*.log



    This tutorial we learned to

    • Seamlessly automate Data Guard associations between diverse ExadataCloud@Customer systems. 
    • leverage OCI CLI & JSON templates to discover its extensive utility beyond compute services.
    • Additionally, you now have a clear understanding of where to access and how to interpret the logs, essential for troubleshooting potential issues.
    • Hope this will encourage every DBA to start using OCI CLI every day for their administration tasks 

    Thank you for reading

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