qual o sla disponibilidade da instancia do salesforce?

Salesforce’s availability SLA is basically 99.9% uptime or better. 

• That means about 43 minutes of downtime per month (or ~9 hours per year).
• In practice, Salesforce often hits closer to 99.99% uptime, which is about 4 minutes per month (~1 hour per year).
• You can always check your instance’s real-time and historical status at trust.salesforce.com or status.salesforce.com.