GemDB Stats

Visualization and AI-assisted analysis for GemDB (GemStone/S) performance statistics.

GemDB Stats reads the statmon files produced by GemStone's statmonitor utility and lets you explore them three ways:

• A desktop app for macOS, Windows and Linux: a modernized take on the Tcl/Tk VSD 5.x. Browse processes, plot any statistic, compare processes side by side, and ask an AI assistant questions about what you see.
• A web version at gemtalk.github.io/GemDB_Stats: the same app in your browser, with no install. It has everything but the AI assistant, and your file never leaves your machine.
• An MCP server that exposes the same analysis tools to any Model Context Protocol client, so Claude Desktop or Claude Code can work through a statmon file with you.

For a quick look, here's a demo from ESUG 2026 on YouTube.

Features

Files

• Open .out and .out.gz statmon files; large files are parsed off the UI thread with a progress indicator.

Processes and statistics

• Browse every process in the file with its start/end time and sample count; search by name.
• Drill into a process's statistics: description, units, min / max / avg. Search statistics and hide the ones with no data.

Charts

• Plot any statistic as a line chart with a trackball tooltip and crosshair for precise inspection.
• Drag to zoom into a time range; reset with one click.
• MultiChart: overlay statistics from one or several processes on a single chart, with a legend that lets you move a series between the left and right axes or remove it.

Time

• Display timestamps in the file's own time zone, UTC, your system zone, or any named zone; show or hide the year and zone label.

AI assistant

• Ask natural-language questions about the loaded data ("which process did the most page reads?", "walk me through the MFC cycle").
• Built-in analysis guides give the model expert runbooks for common GemStone performance questions.
• Requires your own Anthropic API key. See Using the AI assistant.

Getting started

Download

Grab the latest build for your platform from the Releases page. What's new in each version is in the changelog.

Platform	Install
macOS 12+	Unzip and drag GemDB Stats to Applications. The app is signed and notarized.
Windows	Unzip and run GemDBStats.exe. Keep the data/ folder and DLLs next to it.
Linux	Extract the bundle and run ./gemdb-stats. Needs a GTK 3 runtime (libgtk-3-0).

Or skip the download and use the web version in your browser.

Open a statmon file

Click No file selected in the top bar and pick a .out or .out.gz file.

Then select a process in the top-left table, pick one of its statistics in the table next to it, and the chart appears below. Use Start MultiChart in the statistics table to overlay several statistics (from the same process or different ones).

Where statmon files come from

Statmon files are written by GemStone's statmonitor utility, which samples the shared page cache statistics of a running stone and its gems. See Monitoring GemStone in the GemStone/S 64 Bit System Administration Guide for how to run it. Both plain and gzip-compressed output are supported.

Using the AI assistant

1. Click Toggle Chat in the top bar to open the assistant panel.
2. Enter your Anthropic API key (sk-ant-...). It is stored locally on this machine only and can be changed later with Set API key.
3. Ask a question. The assistant uses the in-app MCP tools to query the loaded file and streams its answer back.

You bring your own API key, so data from the loaded file goes directly to Anthropic under your account — how it's handled is between you and Anthropic.

Using the MCP server standalone

The same analysis tools are available as a standalone MCP server that speaks stdio. It needs the Dart SDK (or Flutter, which bundles it).

git clone https://github.com/GemTalk/GemDB_Stats.git
cd GemDB_Stats/mcp
dart pub get

Then point your client at bin/vsd_mcp.dart. For Claude Desktop, add to claude_desktop_config.json:

{
  "mcpServers": {
    "vsd": {
      "command": "dart",
      "args": ["run", "/absolute/path/to/GemDB_Stats/mcp/bin/vsd_mcp.dart"]
    }
  }
}

For Claude Code:

claude mcp add vsd -- dart run /absolute/path/to/GemDB_Stats/mcp/bin/vsd_mcp.dart

Optionally pass a statmon file path as a final argument to load it at startup; otherwise ask the model to call load_file. The full tool list and details are in mcp/README.md.

Embedding

The web build can run inside another page, such as a VS Code webview, with the host page choosing the file to show. See docs/embedding.md.

Contributing

See CONTRIBUTING.md for setting up, running the checks and opening a pull request, and docs/releasing.md for publishing a release.