SQL Server 18056 error solution

Solution:
0. First, check whether the database has a deadlock.
1. The most direct way is to increase the size of the IIS connection pool.
2. Find a large session request in the program and modify the code.
3. Restrict the maximum number of IIS processes and set the connection pool size based on daily running conditions (not recommended, mandatory)
4. Restrictions on SQL session at the Database end: SQL firewall or database restrictions on persistent connections (not recommended, mandatory, no way)