What are the details of the Salesforce SLA, specifically the maximum downtime?
Not exactly what you asked for, but have a look at http://trust.salesforce.com/trust/status/ to see historical server status.
From the Master Service Agreement as at May 2016
3.1. Provision of Purchased Services. We will (a) make the Services and Content available to You pursuant to this Agreement and the applicable Order Forms, (b) provide applicable SFDC standard support for the Services to You at no additional charge, and/or upgraded support if purchased, (c) use commercially reasonable efforts to make the online Services available 24 hours a day, 7 days a week, except for: (i) planned downtime (of which We shall give advance electronic notice as provided in the Documentation), and (ii) any unavailability caused by circumstances beyond Our reasonable control, including, for example, an act of God, act of government, flood, fire, earthquake, civil unrest, act of terror, strike or other labor problem (other than one involving Our employees), Internet service provider failure or delay, Non-SFDC Application, or denial of service attack.
From Proven reliability
Our track record speaks for itself: Salesforce1 Platform has a proven 99.9+ percent uptime record for years. To ensure maximum uptime and continuous availability, Salesforce1 Platform provides redundant data protection and the most advanced facilities protection available, along with a complete data recovery plan.
You should contact your AE [Account Executive] for their official uptime document.
Answers from third parties
From Top 9 Reasons Why You Should Switch from Salesforce.com to Salesboom.com. (Could be heavily biased)
[Salesforce] has never taken steps to offer a service guarantee
From CRM Online VS SalesForce.com (again, probably biased but potentially correct)
NO SERVICE LEVEL AGREEMENT (SLA)
Salesforce.com does not offer a service level agreement.
The FUD that the competition tries to bring to the table by saying that salesforce.com has no SLA is missing the bigger picture; salesforce.com has a double-redundant network that allows them to transfer traffic to a backup or backup-backup set of hardware in mere hours. It would take a national disaster that covers the entire continent of North America to bring them down (although we'd have bigger problems at that point). No competitor I know of brings *that* offer to the table.
@sfdcfox. Agreed. Those last two articles need to be read with a good degree of skepticism as they are pushing alternative products and are clearly biased in their opinions. From the perspective of answering the question. There isn't a SLA for Salesforce.
@sfdcfox can we believe that there is no SLA for Salesforce's Bluechip enterprise clients, I find that hard to grasp, especially now that it being recognised as a platform company not just CRM. I would really like to know what time duration assurance SaleForce commits to getting a service back online/rerouted. If I was a large enterprise I would typically insist on SLA's for this event type in order to mitigate risk to the business continuity.
@Bartley MSA P3.1: "We will ... (c) use commercially reasonable efforts to make the online Purchased Services available 24 hours a day, 7 days a week..." and they also mention that a failure for them to meet their commitments can allow clients to terminate their contract (P9.2, P12.3, 12.4). I've heard that there's a way to get an SLA if you negotiate for one; supposedly some of the larger clients do have one.
I love this comment on Salesboom website about the app exchange `All applications a company adds to their Salesforce.com platform are provided by Salesboom.com as features` pure BS......
What regarding performances degradation?
On trust.salesforce.com it is explicitly declared that if the average of the transactions goes over 0.5 for 2 minutes consecutively, this is considered a performance degradation in the current status, and if it is for 10 minutes consecutively is a performance degradation tracked in the historical section.
Is there any SLA about Performance degradation?