Oracle Source Setup Guide #

Follow the instructions below to set up a replication pipeline from your Oracle database to your destination using Arcion’s Oracle connector.

Note: The first five steps (I-V) describe how to prepare the Oracle Database for replication. You must execute these steps in an Oracle client. The remaining steps (VI-VIII) allow you to configure Replicant.

I. Obtain the JDBC Driver for Oracle #

Replicant requires the JDBC driver for Oracle as a dependency. To obtain the appropriate driver, follow the steps below:

Go to the Oracle Database JDBC driver Downloads page.
We recommend JDBC Driver 18c and Java 8-compatible driver. So navigate to the Oracle Database 18c Downloads section.
From there, download the Oracle JDBC Driver ojdbc8.jar.
Put the ojdbc8.jar file inside $REPLICANT_HOME/lib directory.

II. Set up Oracle User #

Create a new user for Replicant with the following command:

CREATE USER <USERNAME> IDENTIFIED BY <PASSWORD>
DEFAULT TABLESPACE <user-defined-tablesace>
QUOTA unlimited on <user-defined-tablespace>
TEMPORARY TABLESPACE TEMP;

Provide the create session permission:
```
GRANT CREATE SESSION TO <USERNAME>;
```
Grant the select permission for all the tables that are part of the replication:
```
GRANT SELECT ON <TABLENAME> TO <USERNAME>;
```
OR

The select permission can be granted on all of the tables
```
GRANT SELECT ANY TABLE TO <USERNAME>;
```

III. Set up Change Data Capture (CDC) #

Enable ARCHIVELOG mode #

To use log-based CDC, the Oracle database must be in ARCHIVELOG mode. To check what mode the database is in, use the ARCHIVE LOG LIST command. To set the database in ARCHIVELOG mode, use the following commands:

SHUTDOWN IMMEDIATE
STARTUP MOUNT
ALTER DATABASE ARCHIVELOG
ALTER DATABASE OPEN

Set permissions #

Once the database is in ARCHIVELOG mode, grant the EXECUTE_CATALOG_ROLE role to use the DBMS_LOGMNR package:
```
GRANT EXECUTE_CATALOG_ROLE TO <USERNAME>
```
Provide the following permissions to allow Replicant to access the START_LOGMNR procedure:
For Oracle 11g
For Oracle version 11g, execute the following command:
```
GRANT SELECT ANY TRANSACTION TO <USERNAME>;
```
For Oracle 12c and above
For Oracle versions 12C and above, execute the following command:
```
GRANT LOGMINING TO <USERNAME>;
```
You also need to provide the following permission to allow Replicant to access v_$logmnr_contents:
For Oracle below 19c
For Oracle versions below 19c, grant the following permissions:
```
GRANT SELECT ON v_$logmnr_contents TO <USERNAME>;
GRANT SELECT ON gv_$archived_log to <USERNAME>;
```
For Oracle 19c and above
For Oracle versions 19C and above, Replicant requires additional access to v_$logfile.:
```
GRANT SELECT ON v_$logmnr_contents TO <USERNAME>;
GRANT SELECT ON gv_$archived_log to <USERNAME>;
GRANT SELECT ON v_$logfile TO <USERNAME>;
```

Enable logs #

You have to enable either primary key or all column logging at either the database level or the table level.

If you use table level logging, you must enable it for the CDC heartbeat table as well.

Database level Supplemental logging #

Enable Force Logging:
```
ALTER DATABASE FORCE LOGGING
```

Enable PRIMARY KEY logging:

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS

Enable ALL Column logging:

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS

Table level supplemental logging #

PRIMARY KEY logging

ALTER TABLE <TABLE_NAME> ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS

ALL Column logging

ALTER TABLE <TABLE_NAME> ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS

If table level logging is enabled, then force logging should not be enabled. We need force logging for database level logging:
```
ALTER DATABASE FORCE LOGGING
ALTER SYSTEM SWITCH LOGFILE
```

The following additional permissions are required:

GRANT SELECT ON gv_$instance TO <USERNAME>;
GRANT SELECT ON gv_$PDBS TO <USERNAME>;
GRANT SELECT ON gv_$log TO <USERNAME>;
GRANT SELECT ON gv_$database_incarnation to <USERNAME>;

Only enable either PRIMARY KEY logging or ALL column logging, not both.

IV. Set up Global Permissions #

Quick Definitions

One Time Access: The granted permission is only required for the initial data load (snapshot) and for reinit operations (snapshots of newly added tables). The permission can be revoked after the necessary operation is complete.
Continuous Access: The granted permission is required throughout the replication process.

Provide the following privilege for one time access:
```
GRANT SELECT ON DBA_SEGMENTS TO <USERNAME>;
```

Provide the following continuous access permissions; these are necessary during snapshot as well as continious real-time replication:

GRANT SELECT ON gv_$database TO <USERNAME>;
GRANT SELECT ON gv_$transaction TO <USERNAME>;
GRANT SELECT ON gv_$session TO <USERNAME>;--Not required for replicant release 20.8.13.7 and above

Grant the following continuous access permission for the tables involved in Replication:
```
GRANT FLASHBACK ON <TABLE_NAME> TO <USERNAME>;
```
OR

Enable Flashback for all tables
```
GRANT FLASHBACK ANY TABLE TO <USERNAME>;
```

Provide access to the below system views for schema migration:

GRANT SELECT ON ALL_TABLES TO <USERNAME>;
GRANT SELECT ON ALL_VIEWS TO <USERNAME>;
GRANT SELECT ON ALL_CONSTRAINTS TO <USERNAME>;
GRANT SELECT ON ALL_CONS_COLUMNS TO <USERNAME>;
GRANT SELECT ON ALL_PART_TABLES TO <USERNAME>;
GRANT SELECT ON ALL_PART_KEY_COLUMNS TO <USERNAME>;
GRANT SELECT ON ALL_TAB_COLUMNS TO <USERNAME>;
GRANT SELECT ON SYS.ALL_INDEXES TO <USERNAME>;
GRANT SELECT ON SYS.ALL_IND_COLUMNS TO <USERNAME>;
GRANT SELECT ON SYS.ALL_IND_EXPRESSIONS TO <USERNAME>;

V. Set up Connection Configuration #

From $REPLICANT_HOME, navigate to the connection configuration file:
```
vi conf/conn/oracle.yaml
```

You can store your connection credentials in a secrets management service and tell Replicant to retrieve the credentials. For more information, see Secrets management.

Otherwise, you can put your credentials like usernames and passwords in plain form like the sample below:

type: ORACLE

host: localhost #Replace localhost with your oracle host name
port: 1521 #Replace the default port number 1521 if needed
service-name: IO #Replace IO with the service name of your Oracle Listener

username: 'REPLICANT' #Replace REPLICANT with your username to connect to Oracle
password: 'Replicant#123' #Replace Replicant#123 with the your user's password

max-connections: 30 #Maximum number of connections replicant can open in Oracle
continuous-log-mining: true

If you’re using Oracle 19c, please set continuous-log-mining to false. For more information, see Desupport of the CONTINUOUS_MINE feature of LogMiner.

VI. Set up Filter Configuration #

From $REPLICANT_HOME, navigate to the filter configuration file:
```
vi filter/oracle_filter.yaml
```

In accordance to your replication needs, specify the schema(s)/table(s) which is to be replicated. Use the format explained below:

allow:

  #In this example, data of object type Table in the schema REPLICANT will be replicated
  schema: "REPLICANT"
  types: [TABLE]

  #From the shemca REPLCIANT, only the Orders, Customers, and Returns tables will be replicated.
  #Note: Unless specified, all tables in the schema will be replicated

  allow:
    Orders:
       #Within Orders, only the US and AUS columns will be replicated
       allow: ["US, AUS"]

    Lineitem: #All columns in the table Lineitem  will be replicated without any predicates

    Customers:  
       #Within Customers, only the product and service columns will be replicated as long as they meet the condition C_CUSTKEY < 5000
       allow: ["product", "service"]
       conditions: "C_CUSTKEY < 5000"

Below is the filter file template you must follow:

allow:
  schema: <your_schema_name>
  types: <your_object_type>


  allow:
    your_table_name_1:
      allow: ["your_column_name"]
      conditions: "your_condition"  

    your_table_name_2:

    your_table_name_3:
      allow: ["your_column_name"]
      conditions: "your_condition"

For a detailed explanation of configuration parameters in the filter file, read: Filter Reference

VII. Set up Extractor Configuration #

For real-time replication, you must create a heartbeat table in the source Oracle.

Create a heartbeat table in the schema you are going to replicate with the following DDL:

CREATE TABLE "<schema>"."replicate_io_cdc_heartbeat"(
  "timestamp" NUMBER NOT NULL,
  PRIMARY KEY("timestamp"));

Grant INSERT, UPDATE, and DELETE privileges to the user configured for replication
From $REPLICANT_HOME, navigate to the extractor configuration file:
```
vi conf/src/oracle.yaml
```
The configuration file has two parts:
- Parameters related to snapshot mode.
- Parameters related to realtime mode.
Parameters related to snapshot mode #

The following parameters are specific to Oracle as source:
- fetch-create-sql: This option can be used to apply exact create SQL on source to target.
  
  This parameter is available only for Oracle->Oracle pipeline.
- fetch-create-sql-no-constraints: This option is used to split create table SQL and Primary/Unique/Foreign Key constraints as different SQLs. So as part of schema migration we create tables without constraints and after the snapshot is complete the constraints are applied. Application of constraints post snapshot is configured by applier config init-constraint-post-snapshot.
  
  This parameter is available only for Oracle->Oracle pipeline.
- serialize-fetch-createSql: This option is used to fetch create SQL in serialized manner after fetching table schema.
- serialize-fetch-create-sql-no-constraints: This option is used to fetch SQL of Primary/Unique/Foreign Key constraints in serialized manner.
  
  This parameter is available only for Oracle->Oracle pipeline.
- native-load: With this parameter set, Replicant uses the Oracle Data Pump Export (expdp) utility to load table data instead of JDBC. This enables Replicant to efficiently handle large-scale data. For more information, see Oracle Native Export.
The following configuration parameters are available under native-load:
- enable: true or false. Whether to enable native-load.
- stage-type: The type of staging area. Allowed values are SHARED_FS and ASM. The staging area can either be a shared directory or Oracle ASM.
- directory: The Oracle directory object corresponding to the stage-type. For more information, see Create directory object in Source and Target Oracle.
- path: Full path to the NFS (Network File System) representing the directory shared between Replicant and Oracle.
The following is a sample configuration for snapshot mode:
```
snapshot:
  threads: 16
  fetch-size-rows: 10_000
  verify-row-count: false
  _fetch-exact-row-count: true
  _traceDBTasks: true
#  inf-number-behavior: EXCEPTION   # EXCEPTION, ROUND, CONVERT_TO_NULL
#  flashback-query: true
#  parallel-query: true
#  fetch-user-roles: true

#   native-load:
#     enable: false
#     stage-type: SHARED_FS
#     directory: SHARED_STAGE
#     shared-path: FULL_PATH_TO_NFS #full path to the NFS shared directory 


#   per-table-config:
#   - schema: tpch
#     tables:
#       lineitem1:
#         row-identifier-key: [ORDERKEY, LINENUMBER]
#         extraction-priority: 1 #Higher value is higher priority. Both positive and negative values are allowed. Default priority is 0 if unspecified.
#       lineitem1:
#         row-identifier-key: [ORDERKEY, LINENUMBER]
#        products:
#          per-partition-config:
#          - partition-name: SYS_P461
#            row-count: 0
#          - partition-name: SYS_P462
#            row-count: 0
#          - partition-name: SYS_P463
#            row-count: 1
#          - partition-name: SYS_P464
#            row-count: 3
#        part:
#          row-count: 2000
```
- Supplying split-key in the per-table-config section is not required (and not supported) for Oracle source.
- We strongly recommend that you specify row-identifier-key in per-table-config section for tables not having PK/UK constraints defined on the source Oracle system.
Parameters related to realtime mode #

If you want to operate in realtime mode, you can use the realtime section to specify your configuration. The following Oracle specific parameters are available:
- block-ddl-transaction[v20.09.14.3]: This option blocks fetching logs for DDL operation from Oracle.
- use-current-scn[v20.09.14.8]: In start-postion section, this option allows using current scn value for to start reading realtime operations.
- start-scn[v20.09.14.3]: In start-postion section this option allows using user specified scn value for to start reading realtime operations.
- inter-source-latency-s[v20.10.07.16]: In the start-position section this config option in seconds represents the lag between primary and standby Oracle in case the source-failover feature is enabled.
- log-miner-dict-file[v21.09.17.6]: If specified, this file will be used as the dictionary for log mining instead of using the online dictionary. The file must be accessible by Oracle.
- oldest-active-txn-window-hr[v22.07.19.3]: Specifies the time period in hours up to which Replicant should fetch the oldest transaction SCN.
  
  Default: By default, this parameter is set to 24.
The following is a sample configuration for realtime mode:
```
realtime:
  threads: 4
  _traceDBTasks: true
  #fetch-size-rows: 0
  heartbeat:
    enable: true
    schema: "tpch"
    interval-ms: 10000
    table-name: replicate_io_cdc_heartbeat

  start-position:
    start-scn: 2362927
```
Support for DDL replication #

Replicant supports DDL replication for real-time Oracle source. For more information, contact us.

For a detailed explanation of configuration parameters in the Extractor file, see Extractor Reference.