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Prerequisites

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Standby databases

An Oracle database can be configured with either a physical or a logical standby database for recovery after a production failure. At this time, Streamkap does not support them.
  • Oracle 12c or above, Standard or Enterprise Edition
  • Hostname and Port
  • (single-tenant architecture): Database name
  • (multi-tenant architecture): Container database name (CDB) and pluggable database name (PDB)
  • The Oracle database master user credentials or equivalent

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Oracle Setup

For the Connector to ingest changes from your database it is dependent on Oracle’s redo logs and archive logs. It is important that these redo logs are large enough and, the archive logs are retained for long enough to ensure all changes are captured.

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1. Enable Archive Logs

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Reboot required

When ARCHIVELOG mode is enabled, your Oracle database will be taken offline.
When redo logs fill up, Oracle archives groups of them into archive logs. Archive logs should be retained for at least 24 hours. However, we recommend retaining them for longer. Too short a retention period and changes may not be captured and processed.

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Retention periods and database storage

Archive logs are retained on your database instance using up its storage capacity. It is important to make sure it has enough space, otherwise, performance issues and outages can occur.In general, the more tables (and columns) there are, the more capacity is required. For the Connector, additional capacity is essential because it depends on Oracle’s supplemental logging.To estimate what storage capacity you might need and assuming your Oracle database has supplemental logging enabled, you can look at the last 1 hour of log storage usage and multiply that by the retention period (at least 24 hours) you choose. Here’s an example script for that:
SQL
SELECT
 SUM(BLOCKS * BLOCK_SIZE) bytes, -- usage
 SUM(BLOCKS * BLOCK_SIZE) * 72 estimated_bytes -- assuming 72 hours archivelog retention
  FROM V$ARCHIVED_LOG
 WHERE 
  FIRST_TIME >= SYSDATE-(1/24) -- last hour
  AND 
  DEST_ID=1;
You should set the DB_RECOVERY_FILE_DEST_SIZE parameter to a value that is appropriate for your available disk space. 
-- Replace the {...} placeholders as required
alter system set db_recovery_file_dest_size = {recovery_file_size};
alter system set db_recovery_file_dest = '{recovery_file_location}' scope=spfile;
Then, configure Oracle RMAN to retain backups and archive logs for at least 24 hours. We recommend retaining data for longer. 
RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 3 DAYS;
To enable ARCHIVELOG mode, run this script: 
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;
To confirm if ARCHIVELOG mode has been enabled, run this query: 
archive log list;
If the Database log mode is Archive Mode then it is enabled.

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2. Enable LogMiner

For the Connector to query the redo and archive logs, it is dependent on the Oracle LogMiner utility. To enable that, supplemental logging must be enabled. 
-- Enable database supplement logging
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;
After supplemental logging has been enabled at the database level, you then need to enable table level supplemental logging. 
-- To enable all supplemental logging, run the following SQL statement for each table:
ALTER TABLE {schema}.{table} ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS
To confirm if supplemental logging has been enabled, run this query: 
SELECT NAME, SUPPLEMENTAL_LOG_DATA_MIN FROM V$DATABASE;
If the SUPPLEMENTAL_LOG_DATA_MIN is YES it is enabled.

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2.1) Resize redo logs

An Oracle instance typically starts with three, online redo log files, 50MB each. That is too small and too few; more log files are necessary, and the logs should be resized to at least 1024MB or more, especially for production databases. Before making any changes, run this query to check the current log file sizes: 
SELECT GROUP#, BYTES/1024/1024 SIZE_MB, STATUS FROM V$LOG ORDER BY 1;
GROUP#SIZE_MBSTATUS
150INACTIVE
250INACTIVE
350CURRENT
Also, we need to determine how many log files per group there are and their location. 
SELECT GROUP#, LOCATION FROM V$LOGFILE ORDER BY 1, 2;
GROUP#LOCATIONSTATUS
1/opt/oracle/oradata/ORCLCDB/redo01.logACTIVE
2/opt/oracle/oradata/ORCLCDB/redo02.logINACTIVE
3/opt/oracle/oradata/ORCLCDB/redo03.logUNUSED
Now replace the old log files with new, larger log files. Only INACTIVE and UNUSED groups can be dropped and recreated.

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Log multiplexing

Oracle does support the notion of multiple log files per group known as ‘log multiplexing’. If your database uses this, use a comma-delimited list of filenames to register each log file.
-- Execute these statements as many times as required for existing INACTIVE and UNUSED log groups
-- Replace {group_number} placeholder and {log_location}, using a comma separated list of filenames if database uses log multiplexing
ALTER DATABASE CLEAR LOGFILE GROUP {group_number};
ALTER DATABASE DROP LOGFILE GROUP {group_number};
ALTER DATABASE ADD LOGFILE GROUP {group_number} ('{log_location}') size 1024M REUSE;
Now switch the ACTIVE log so we can drop it. 
ALTER SYSTEM SWITCH LOGFILE;
We need to wait for the database to eventually switch the status of the ACTIVE group to INACTIVE. The switch could take several minutes, so be patient and recheck the size periodically. Once the status reaches INACTIVE, replace the last, old log file and confirm all logs are resized: 
-- Execute these statements as many times as required for existing INACTIVE and UNUSED log groups
-- Replace {group_number} placeholder and {log_location}, using a comma separated list of filenames if database uses log multiplexing
ALTER DATABASE CLEAR LOGFILE GROUP {group_number};
ALTER DATABASE DROP LOGFILE GROUP {group_number};
ALTER DATABASE ADD LOGFILE GROUP {group_number} ('{log_location}') size 1024M REUSE;

SELECT GROUP#, BYTES/1024/1024 SIZE_MB, STATUS FROM V$LOG ORDER BY 1;
GROUP#SIZE_MBSTATUS
11024CURRENT
21024UNUSED
31024ACTIVE
………
Now add additional, new log files as necessary. We suggest starting with 4 additional log files.

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Group numbering and log file sizing

The {group_number} should follow sequentially. There is no benefit to organising log groups in sequences such as 10,20,30 or mixed sizing such as 128MB, 1024MB, 512MB.For example, if the highest group number is 3 and log file /opt/oracle/oradata/ORCLCDB/redo03.log of size 1024MB, the next log file added should be group 4 and log file /opt/oracle/oradata/ORCLCDB/redo04.log of size 1024MB.
-- Execute these statements as many times as required
-- Replace {group_number} placeholder and {log_location}, using a comma separated list of filenames if database uses log multiplexing
ALTER DATABASE ADD LOGFILE GROUP {group_number} ('{log_location}') size 1024M;

SELECT GROUP#, BYTES/1024/1024 SIZE_MB, STATUS FROM V$LOG ORDER BY 1;
GROUP#SIZE_MBSTATUS
11024CURRENT
21024UNUSED
31024ACTIVE
41024INACTIVE
51024INACTIVE
………

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3. Create Database User

Depending on your database architecture, choose the correct script below to create a database user with privileges for the Connector. 
-- Replace {...} placeholders as needed
ALTER SESSION SET CONTAINER=CDB$ROOT;
CREATE USER C##STREAMKAP_USER IDENTIFIED BY {password};

ALTER SESSION SET CONTAINER={PDB};
CREATE TABLESPACE STREAMKAP_LOGMINER_TBS DATAFILE {filename} SIZE 25M AUTOEXTEND ON MAXSIZE UNLIMITED;
ALTER USER C##STREAMKAP_USER DEFAULT TABLESPACE STREAMKAP_LOGMINER_TBS;
ALTER USER C##STREAMKAP_USER QUOTA UNLIMITED ON STREAMKAP_LOGMINER_TBS;

-- Grant permissions
GRANT CREATE SESSION TO C##STREAMKAP_USER CONTAINER=ALL; 
GRANT SET CONTAINER TO C##STREAMKAP_USER CONTAINER=ALL; 

-- Allows the Connector to use LogMiner
GRANT LOGMINING TO C##STREAMKAP_USER CONTAINER=ALL;

-- Flashback queries used for performing initial snapshots of the data
GRANT FLASHBACK ANY TABLE TO C##STREAMKAP_USER CONTAINER=ALL; 
GRANT SELECT ANY TRANSACTION TO C##STREAMKAP_USER CONTAINER=ALL; 

-- Required for schema history when performing initial snapshots
GRANT SELECT_CATALOG_ROLE TO C##STREAMKAP_USER CONTAINER=ALL; 
GRANT EXECUTE_CATALOG_ROLE TO C##STREAMKAP_USER CONTAINER=ALL; 

-- Connector creates a table for explicitly managing the flushing of internal log buffers (LGWR)
GRANT CREATE TABLE TO C##STREAMKAP_USER CONTAINER=ALL;

GRANT CREATE SEQUENCE TO C##STREAMKAP_USER CONTAINER=ALL; 

-- Grant the Streamkap user permission to read each schema and table you wish to sync
ALTER SESSION SET CONTAINER={PDB};
GRANT SELECT ON {schema}.{table} TO C##STREAMKAP_USER CONTAINER=ALL;
-- Alternatively, you can grant access to all
-- GRANT SELECT ANY TABLE TO C##STREAMKAP_USER CONTAINER=ALL;

-- Grant the Streamkap user access to the DBA_EXTENTS, DBA_TABLESPACES, DBA_SEGMENTS, and TRANSACTION system views. 
GRANT SELECT ON DBA_EXTENTS TO C##STREAMKAP_USER;
GRANT SELECT ON DBA_TABLESPACES TO C##STREAMKAP_USER;
GRANT SELECT ON DBA_SEGMENTS TO C##STREAMKAP_USER;
GRANT SELECT ANY TRANSACTION TO C##STREAMKAP_USER;

-- Grant the Streamkap user permission to run LogMiner
ALTER SESSION SET CONTAINER=CDB$ROOT;
GRANT SELECT ON SYS.V_$DATABASE TO C##STREAMKAP_USER;
GRANT SELECT ON SYS.V_$PARAMETER TO C##STREAMKAP_USER;
GRANT SELECT ON SYS.V_$ARCHIVED_LOG TO C##STREAMKAP_USER;
GRANT SELECT ON SYS.V_$ARCHIVE_DEST TO C##STREAMKAP_USER;
GRANT SELECT ON SYS.V_$LOGMNR_CONTENTS TO C##STREAMKAP_USER;
GRANT EXECUTE ON DBMS_LOGMNR TO C##STREAMKAP_USER;
GRANT EXECUTE ON DBMS_LOGMNR_D TO C##STREAMKAP_USER;
GRANT SELECT ANY TRANSACTION TO C##STREAMKAP_USER;
GRANT EXECUTE_CATALOG_ROLE TO C##STREAMKAP_USER;

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4. Enable Snapshots

To backfill your data, the Connector needs to be able to perform Snapshots (See Snapshots & Backfilling for more information). To enable this process, a table must be created for the Connector to use. Depending on your database architecture, choose the correct script below.
Please create the signal table with the name STREAMKAP_SIGNAL. It will not be recognised if given another name.
-- Replace {...} placeholders as needed

ALTER SESSION SET CONTAINER={PDB};

-- Create a local (PDB) user
CREATE USER STREAMKAP_USER IDENTIFIED BY {password};
GRANT CREATE SESSION TO STREAMKAP_USER; 
GRANT SET CONTAINER TO STREAMKAP_USER;

ALTER USER STREAMKAP_USER DEFAULT TABLESPACE STREAMKAP_LOGMINER_TBS;
ALTER USER STREAMKAP_USER QUOTA UNLIMITED ON STREAMKAP_LOGMINER_TBS;

-- Create the table
CREATE TABLE STREAMKAP_USER.STREAMKAP_SIGNAL (
  id VARCHAR2(255) PRIMARY KEY, 
  type VARCHAR2(32) NOT NULL, 
  data VARCHAR2(2000) NULL
);

-- Grant necessary privileges on the table to the common user
GRANT SELECT, UPDATE, INSERT, DELETE ON STREAMKAP_USER.STREAMKAP_SIGNAL TO C##STREAMKAP_USER;

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Streamkap Setup

  • Go to Sources and choose Oracle
  • Input the following information:
    • Name - A unique and memorable name for this Connector
    • Hostname - The database endpoint
    • Port (optional) - The database port
    • Username (case sensitive) - STREAMKAP_USER or the username you chose
    • Password - The database user’s password
    • Signal Table Schema - Streamkap will use a collection in this schema to manage snapshots e.g. public. See Enable Snapshots for more information
    • Heartbeat - Essential for low volume, pluggable databases. See Oracle Heartbeats (CDB Multi-Tenant)
      • Heartbeat Table Schema - Streamkap will use a table in this schema to manage heartbeats. Usually this is the same as the Signal Table Schema
    • Database - The database name (single-tenant architecture) or container database name (multi-tenant architecture)
    • Pluggable Database (optional, multi-tenant architecture only) - The pluggable database name
    • Connect via SSH Tunnel. See SSH Tunnel
    • Advanced Parameters
      • Represent Binary Data As (Default bytes)
    • Add Schemas/Tables. Can also bulk upload here. The format is a simple list of each schema or table per row saved in csv format without a header.
  • Click Save
The connector will take approximately 1 minute to start processing data.

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Frequently Asked Questions

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Why does the Connector need CREATE TABLE privileges?

Oracle has a background process called the “Log Writer” or LGWR for short. Logs are written to an in-memory buffer first, and then the LGWR writes them to disk. The Connector needs to keep track of the last recorded system change number (SCN) that the LGWR process records for each committed transaction. It’s best to persist that SCN somewhere outside of the Connector so it creates a very small, 1 column table named LOG_MINING_TABLE. If the Connector fails, it can use the last recorded value from that table to recover.

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Do I need to resize my redo logs for a database with low data volume and traffic?

We recommend it because the supplemental logging configuration from earlier in this guide will increase the amount of data in the redo logs, data that’s required for tracking changes to your data, including it’s schema. We would also recommend for databases with low traffic to also enable the heartbeats feature explained here: Oracle Heartbeats

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Multi-tenant Architecture

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How do I find the Container and pluggable database names?

Connect to the database and run this script to list the available container (CDB) and pluggable database (PDB) names. 
SELECT NAME, CDB, CON_ID FROM V$DATABASE ORDER BY CON_ID;
For the Container database names, the CDB column should show YES.

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Can I create an Oracle local user instead?

At this time, no. The Connector makes calls to LogMiner APIs from within the root database. Additionally, it consults several V$ tables which are not available from within a PDB.