Db2 to Cassandra
real-time replication
TwinCommit replicates IBM Db2 to Apache Cassandra in real time by reading the Db2 transaction log and applying every committed change exactly once and in commit order. Use it to serve Db2 data from Cassandra at scale without dual writes, with no triggers or capture tables on the source.
Db2
log reader
commit-ordered · exactly-once
Cassandra
native writer
How capture works on Db2
TwinCommit reads the Db2 recovery log through the native log read API and decodes row images itself. No SQL Replication, no Q Replication, no CD tables, no triggers and no capture agents are installed on the source.
Prerequisites
- ✓Archive logging enabled (LOGARCHMETH1)
- ✓DATA CAPTURE CHANGES on each replicated table
- ✓A primary key or unique index on each replicated table
- ✓DBADM (or SYSADM) for the capture user
How apply works on Cassandra
Batched upserts and deletes use the source commit timestamp as the Cassandra write timestamp, so replays are idempotent and newer data always wins.
Requirements
- ✓cdc_enabled: true in cassandra.yaml
- ✓WITH cdc = true on replicated tables
- ✓Agent sidecar or shared volume access to cdc_raw on each node
Setup
Set up Db2 → Cassandra in four steps
- 1
Prepare Db2
Run twincommit check. It verifies archive logging enabled (logarchmeth1) and the other prerequisites, and prints the exact fix for anything missing.
- 2
Point at Cassandra
Add a target block for Cassandra. TwinCommit can generate target DDL with twincommit ddl -apply.
- 3
Snapshot
twincommit snapshot copies each table under a brief share lock and records the exact log position.
- 4
Stream
twincommit run streams every committed change from that position, exactly once and in commit order.
source:
type: db2
database: PRODDB
user: ${SRC_USER}
password: ${SRC_PASSWORD}
target:
type: cassandra
contact_points: [cass-1, cass-2, cass-3]
keyspace: replica
consistency: LOCAL_QUORUM
tables:
- source: SALES.ORDERS
- source: SALES.ORDER_LINES
exclude_columns: [INTERNAL_NOTES]Db2 to Cassandra replication FAQ
How does TwinCommit replicate Db2 to Cassandra?
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TwinCommit reads changes from the Db2 transaction log, buffers them per transaction, and applies each committed transaction to Cassandra in commit order. Batched upserts and deletes use the source commit timestamp as the Cassandra write timestamp, so replays are idempotent and newer data always wins.
Does Db2 to Cassandra replication need triggers or capture tables?
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No. TwinCommit reads the Db2 log directly and creates no objects in the source database.
Is Db2 to Cassandra replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same Cassandra transaction as the data, so a crash or restart never loses or duplicates a transaction.
What Db2 versions are supported?
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Db2 LUW 11.1, 11.5, 12.1 · Db2 for z/OS 12 and 13 · Db2 on Cloud (target).
Stream Db2 to Cassandra today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.