Goldengate

The previous investigation had an abend and an error code to start from. This one is harder precisely because there isn’t one — Replicat is running, lag is zero, the report file is clean, and yet a nightly reconciliation job is flagging rows where the target’s EMAIL column contains what looks like a phone number. When replication looks completely healthy but the data is wrong, the investigation has to start from the data itself, not from a log. ...

The previous two posts walked through specific investigations. This one is the reference behind them — the Logdump commands worth knowing well, plus the tricks that separate a five-minute trail file check from an hour of scrolling through raw hex. 1. Session Setup: Get Readable Output First The default Logdump view is barely usable — raw hex with minimal structure. Every session should start the same way: Logdump 1 > OPEN ./dirdat/rt000412 Logdump 2 > GHDR ON Logdump 3 > DETAIL DATA Logdump 4 > USETOKEN ON Command What it does Skip it and you get GHDR ON Shows the record header — timestamp, RBA, operation type Records with no context on when/what DETAIL DATA Shows actual column values, decoded Raw hex offsets only DETAIL ON (without DATA) Shows column names/lengths but not values Structure without content — useful when scanning fast USETOKEN ON Decodes GoldenGate’s internal tokens (source DB type, CSN, transaction ID) Tokens print as unreadable hex Trick: if you’re scanning hundreds of records just to find where a table’s activity starts, use DETAIL ON without DATA — it’s faster to read and enough to spot the record you actually want, then flip to DETAIL DATA once you’re near it. ...

Classic GoldenGate has one entry point: GGSCI. Microservices has three — adminclient (a scriptable CLI purpose-built for MA), direct REST calls, and the Service Manager Web UI. This post covers the CLI and REST paths for the operations you’ll do constantly: connecting to a deployment, seeing what’s running, and setting up database connections that Extract and Replicat processes can reuse. 1. Connecting with Adminclient adminclient ships alongside the Microservices install and is the closest equivalent to opening GGSCI — except it talks to the Service Manager over REST instead of operating on local files directly. ...

GoldenGate replication has three stages, and each one fails differently under load: Extract can fall behind on redo mining, the Pump/Distribution path can saturate the network, and Replicat can bottleneck applying changes to the target. Tuning the wrong stage wastes time and rarely moves the needle — the first job is always figuring out where the lag actually is. 1. Locate the Bottleneck Before Touching Parameters Every tuning exercise starts with LAG and INFO, not with changing parameters blindly. ...

When Replicat abends, the error message tells you what failed, but rarely why. INFO REPLICAT and the report file point you at a table and an error code — to actually understand the data that caused it, you need to open the trail file itself with Logdump, GoldenGate’s trail-file inspection utility. This post walks through a real investigation end to end, from the initial abend to the actual root cause sitting inside the raw record bytes. ...

This article picks up where the networking and storage setup left off. The Proxmox host (pve01.lab.example.com) is running with two VLAN-aware bridges, a ZFS mirror pool (vmpool), and shared ASM zvols already created. We now create all ten VMs using the qm CLI, configure shared storage for RAC, and verify each group before installing Oracle software. 1. VM Inventory and Resource Plan VM ID Hostname Role vCPU RAM OS Disk Notes 100 rac1-node1 RAC Cluster 1, Node 1 8 32 GB 80 GB Shared ASM 101 rac1-node2 RAC Cluster 1, Node 2 8 32 GB 80 GB Shared ASM 110 rac2-node1 RAC Cluster 2, Node 1 8 32 GB 80 GB Shared ASM 111 rac2-node2 RAC Cluster 2, Node 2 8 32 GB 80 GB Shared ASM 120 oms01 Enterprise Manager OMS 1 4 24 GB 80 GB + 200 GB data Primary OMS 121 oms02 Enterprise Manager OMS 2 4 24 GB 80 GB + 200 GB data Secondary OMS 130 okv01 Oracle Key Vault Primary 4 16 GB 80 GB TDE key store 131 okv02 Oracle Key Vault Secondary 4 16 GB 80 GB Paired node 140 ogg01 GoldenGate Microservices (Extract) 4 16 GB 80 GB + 200 GB trail OGG 23ai MA 141 ogg02 GoldenGate Microservices (Replicat) 4 16 GB 80 GB + 200 GB trail OGG 23ai MA Total: 56 vCPU / 240 GB RAM — host has 32 threads and 256 GB. vCPU is intentionally overcommitted (lab workloads are not all active simultaneously). RAM headroom: 16 GB for Proxmox host. ...

Active-active replication — where two or more databases accept writes simultaneously and replicate to each other — is one of the most powerful but also most operationally complex GoldenGate topologies. Without a robust conflict detection and resolution (CDR) strategy, you will silently corrupt data on one or both sides. This article covers CDR mechanics, built-in GoldenGate resolution handlers, and architectural patterns that minimise conflict occurrence in the first place. Why Conflicts Occur In a bidirectional topology, any row can be updated on either site concurrently. A conflict occurs when: ...

Oracle GoldenGate ships in two distinct deployment architectures: the Classic Architecture (the original GGSCI-based model) and the Microservices Architecture (introduced in 18c, fully mature from 21c). Both replicate data using the same trail-file and process model under the hood, but they differ substantially in how processes are deployed, managed, and monitored. Choosing the wrong one for your use case adds unnecessary operational complexity. The Fundamental Difference Dimension Classic Microservices Management interface GGSCI command-line REST API + Web UI Process model OS-level processes managed by Manager Microservices managed by Service Manager Configuration storage Flat parameter files (.prm) Internal repository (configurable) Deployment unit Single installation per host Service-based; multiple deployments per host OCI/Cloud-native fit Requires custom automation Native REST/API; integrates with OCI GoldenGate Security Parameter-file credentials Credential store + wallet Multi-tenancy (CDB) Limited Full PDB-level pipeline isolation Classic Architecture: Operational Model In Classic, the Manager process is the parent for all Extract, Pump, and Replicat processes. You interact with the system via GGSCI (GoldenGate Software Command Interface). ...

Migrating an Oracle database to OCI involves more than moving data — it requires selecting the correct migration toolchain, designing for cutover, and managing risk. Oracle provides multiple migration paths, and choosing incorrectly leads to extended downtime or data integrity issues. This article compares the major approaches and provides decision criteria. Migration Approach Decision Tree Is downtime during migration acceptable? ├── YES (hours or more acceptable) │ ├── Database size < 1 TB → Data Pump (expdp/impdp) over network or pre-stage to Object Storage │ └── Database size > 1 TB → RMAN duplicate or backup/restore to OCI Object Storage └── NO (near-zero or zero downtime required) ├── Source is Oracle → Zero Downtime Migration (ZDM) with GoldenGate └── Source is non-Oracle → OCI Database Migration Service (DMS) Zero Downtime Migration (ZDM) Oracle ZDM is the recommended tool for migrating Oracle databases to OCI with minimal or zero downtime. It orchestrates a combination of RMAN (initial bulk copy) + GoldenGate (ongoing replication during migration) in an automated workflow. ...

Oracle GoldenGate is the industry standard for heterogeneous, real-time data replication and change data capture (CDC). Despite being in use for decades, its internal mechanics are frequently misunderstood, leading to poorly tuned deployments that bottleneck at the wrong layer. This article dissects the architecture from the redo log all the way to the target apply. Architecture Overview A GoldenGate pipeline has three logical tiers: Capture — the Extract process mines redo/archive logs on the source database. Distribution — the Data Pump (a secondary Extract) reads local trail files and transmits them to a remote trail on the target host. Apply — the Replicat process reads the remote trail and applies changes to the target database. Each tier operates independently, connected only through trail files — sequential, compressed binary files that serve as a persistent, durable queue between processes. ...