VARCHAR2(4000) means 4000 bytes, not characters. Most people know this. What's less obvious: VARCHAR2(4000 CHAR) doesn't guarantee 4000 characters either.
Under the default MAX_STRING_SIZE=STANDARD, the hard column cap is 4000 bytes regardless of whether you declared BYTE or CHAR. In AL32UTF8, a Chinese character takes ~3 bytes, so VARCHAR2(4000 CHAR) on a column storing CJK text will fail once the actual byte count exceeds 4000 — around ~1333 characters in.
To actually store 4000 CJK characters in a single VARCHAR2, the instance needs MAX_STRING_SIZE=EXTENDED (12c+), which raises the limit to 32767 bytes. This is not the default — not even in 19c — and it's a one-way migration that requires running utl32k.sql in upgrade mode. Oracle keeps it off by default precisely because it changes data dictionary behavior and breaks compatibility.
Quick check for your instance:
SELECT value FROM v$parameter WHERE name = 'max_string_size';
STANDARD = 4000-byte ceiling. EXTENDED = 32767-byte ceiling.
When scripting with Oracle SQLcl, the startup banner (version, copyright, connection info) clamps your output. The -S (silent) flag suppresses all of it:
sql -S user/password@connect_string @script.sql
This gives you clean output suitable for piping or log capture.
For even more control inside the session, pair it with:
set heading off
set feedback off
set pagesize 0
set echo off
-S is the entry-level switch. The set commands handle the rest.
AWS console offers three ways to duplicate an EC2 instance, differing in whether disk data is carried over.
Create AMI (recommended, full clone) — preserves the system disk, installed software, and all configuration.
In the EC2 console, select the target instance → Actions → Image and templates → Create image. Wait for the AMI status to become available (a few minutes to tens of minutes), then go to AMIs → select it → Launch instance from AMI. Adjust instance type, subnet, Security Group as needed.
Launch More Like This (fastest, no data) — copies only instance configuration (type, SG, subnet, tags). The system disk is brand new.
Actions → Image and templates → Launch more like this. The Launch page opens with config pre-filled; confirm and launch. Good for stateless instances, e.g. web servers initialized via userdata.
Launch Template — if the original instance had a Launch Template saved, launch directly from it. EC2 → Launch Templates → select template → Actions → Launch instance from template.
Use AMI for most cases. Use Launch More Like This when you only need the same specs with a clean disk.
AWS 控制台里有三种复制 EC2 的方式，区别在于是否携带磁盘数据。
创建 AMI（推荐，完整克隆） — 保留系统盘数据、已安装软件和所有配置。
EC2 控制台选中目标实例 → Actions → Image and templates → Create image。等 AMI 状态变为 available（几分钟到几十分钟），再到 AMIs 页面选中它 → Launch instance from AMI，按需调整 instance type、subnet、Security Group 即可。
Launch More Like This（最快，但不含数据） — 只复制实例规格配置（type、SG、subnet、tags），系统盘是全新的。
Actions → Image and templates → Launch more like this，进入 Launch 页面时配置已预填好，确认启动就行。适合无状态实例，比如用 userdata 初始化的 web server。
Launch Template — 如果原实例之前保存过 Launch Template，可以直接从模板启动。EC2 → Launch Templates → 选模板 → Actions → Launch instance from template。
大多数场景用 AMI，只需要同规格全新系统时用 Launch More Like This。
In development, your frontend runs on localhost:5173 and your API server on localhost:3000. The browser blocks cross-origin requests — that's CORS. Vite's dev proxy solves this by forwarding /api/* requests to the backend, making them look same-origin to the browser:
// vite.config.ts
server: {
proxy: {
'/api': 'http://localhost:3000'
}
}
In production this proxy disappears. The built frontend is just static files (HTML/JS/CSS) — no port, no process. Nginx or a CDN serves them, and reverse-proxies /api/* to the backend the same way Vite did in dev:
user → Nginx :80
├── /api/* → backend :3000
└── /* → dist/ static files
One port from the user's perspective, no CORS issue. The backend port is always real and needed; the frontend "port" only exists during development because Vite's dev server is a live process.