Companies with a NetSuite account have to pay extra to have access to a sandbox version, where they take a snapshot of your current database and copy it to a test server (on demand, usually takes a few days to a week). This can be a great way to test out incremental modifications to your existing set up, and can give you a chance to see if it conflicts with other customizations.
Once you purchase the sandbox account from NetSuite, the administrator of the production system has to request a REFRESH of the sandbox account, which essentially creates a copy of the production database at that time. This process typically takes about 1-2 business days. During the refresh request, you can select to only allow ADMINISTRATORS access to the sandbox account or allow all users to access the sandbox. Any workflows which trigger an e-mail notification to recipients will be prefixed with the [SANDBOX] disclaimer, allowing all parties to quickly differentiate notifications from the production account.
As with most things from NetSuite, the sandbox account is not cheap, but if you do any amount of customization in your system, usually well worth it.
The sandbox account does run significantly slower than a live account. Sometimes a saved search or report will time out, but most of the time the slowness is a minor inconvenience. I haven´t run into any situations where I was unable to complete my testing in the sandbox account, but most of the time it did take longer than it would have otherwise.
I would recommend the sandbox for companies who have invested a lot into customization and scripting, and need to test complex bundles and solutions on a regular basis. Keep in mind that NetSuite gives you access to a beta copy of your account twice a year for several weeks, which works exactly like the sandbox. If your testing needs can be satisfied with a combination of the beta and a test drive account, then the sandbox might not be necessary.
The NetSuite connection represents a single NetSuite account, including login credentials. If you have multiple accounts or sandbox instances, you need to use a separate connection for each and configure the URL accordingly. You can pair a single connection with different NetSuite operations to perform a unique action against a NetSuite account.
In September 2012 NetSuite began hosting new customer accounts in multiple data centers. The URL to be used for access depends upon the data center hosting each NetSuite account. For example, it could be webservices.netsuite.com or webservices.na1.netsuite.com. All that you need to do is enter the default URL, https://webservices.netsuite.com/services/NetSuitePort_<year>_<version_number>, in the NetSuite connection. The NetSuite connector automatically discovers the correct URL for access to your NetSuite account. This automatic lookup works with any NetSuite version that you select. NetSuite treats Beta URLs and sandbox URLs differently, so the automatic lookup does not occur when you use them.