Oracle Data Guard Apply Lag Monitor

Overview

This repository contains a shell script used to monitor Oracle Data Guard Apply Lag in mission-critical RAC and Exadata environments.
The script collects the apply lag value directly from dynamic performance views and can be used for scheduled monitoring, alerting, or integration with observability tools.

It was designed to help DBAs detect delays in log apply on physical standby databases, enabling faster troubleshooting and improving Data Guard resiliency.

Features

• Retrieves real-time apply lag using v$dataguard_stats
• Supports Oracle RAC (multi-thread) and standalone configurations
• Validates database role (Primary vs. Standby)
• Outputs numeric and human-readable values
• Easy to integrate with:
  • cron jobs
  • monitoring dashboards
  • alerting pipelines (email, Slack, webhooks, etc.)
• Works on Exadata and on-prem Oracle deployments

Example query used

The script queries:

SELECT value, time_computed
FROM v$dataguard_stats
WHERE name = 'apply lag';

Requirements

• Linux environment
• Bash
• SQL*Plus client installed
• Oracle environment configured (ORACLE_HOME, ORACLE_SID, PATH)
• User with permission to query V$ views (SYS, SYSDG, or a user with SELECT_CATALOG_ROLE)

Usage

1. Clone the repository:

    git clone https://github.com/guborges/Data-Guard-Apply-Lag-Monitor.git
    cd Data-Guard-Apply-Lag-Monitor
   

2. Edit database connection variables inside the script:

    vi dg_apply_lag.sh
   

3. Make the script executable:

    chmod +x dg_apply_lag.sh
   

4. Run the monitor:

    ./dg_apply_lag.sh
   

Script output example

Apply Lag: +00 00:00:02
Time Computed: 2025-12-10 14:33:21
Status: OK – Apply is synchronized.

If lag exceeds predefined thresholds, the script can be easily extended to trigger alerts or integrate with external monitoring/alerting tools.

File structure

Data-Guard-Apply-Lag-Monitor/
├── dg_apply_lag.sh
└── README.md

Notes

This script is used in real-world Exadata Cloud@Customer environments where Data Guard apply performance is mission-critical.
It provides a lightweight and reliable way to monitor synchronization between primary and standby databases.

License

MIT License