Improve error message when write operation is performed in snapshot execution

Detail name	Value
Changelog Number	10651
Type	Bug
Status	Open
Affected Versions	Exasol 6.2.0

Background

Write operations are not allowed in Snapshot Transaction mode. 

When a user performs a write operation, the session crashes and restarts with an unclear error message "Internal server error, transaction was rolled back."

How to reproduce

Statements like below perform a write operation in snapshot transaction mode which is not allowed.

/*snapshot execution*/ create schema sch;

Fix

The error handling for unsupported write operations in snapshot mode will be improved. A clear error message indicating the problem will be provided.

[Code: 0, SQL State: 40001] GlobalTransactionRollback msg: No write operation allowed in snapshot mode. (Session: 1674220375006707712)