1. A method implemented by one or more computing devices, the method comprising: receiving a query request for data stored in at least two different databases, the query request based at least in part on a business model, the business model comprising one or more business elements; generating a uniform query that masks a difference among the at least two different databases by converting the query request into one or more execution modes that match with the at least two different databases to be queried based at least in part on a conversion rule between the business model and a storage model, the storage model comprising attribute information of the at least two different databases to be queried and the conversion rule comprising a corresponding relationship between the one or more business elements and one or more attributes in the at least two different databases to be queried; accessing the at least two different databases according to the one or more execution modes; and upon determining that an amount of concurrent accesses to one of the at least two different databases according to the one or more execution modes exceeds a predetermined amount, delaying a subsequent access to the one of the at least two different databases, or accessing a backup database, if available, of the one of the at least two different databases, the backup database having less concurrent accesses than the one of the at least two different databases.
1. A method implemented by one or more computing devices, the method comprising: receiving a query request for data stored in at least two different databases, the query request based at least in part on a business model, the business model comprising one or more business elements; generating a uniform query that masks a difference among the at least two different databases by converting the query request into one or more execution modes that match with the at least two different databases to be queried based at least in part on a conversion rule between the business model and a storage model, the storage model comprising attribute information of the at least two different databases to be queried and the conversion rule comprising a corresponding relationship between the one or more business elements and one or more attributes in the at least two different databases to be queried; accessing the at least two different databases according to the one or more execution modes; and upon determining that an amount of concurrent accesses to one of the at least two different databases according to the one or more execution modes exceeds a predetermined amount, delaying a subsequent access to the one of the at least two different databases, or accessing a backup database, if available, of the one of the at least two different databases, the backup database having less concurrent accesses than the one of the at least two different databases. 7. The method of claim 1 , wherein the query request comprises a storage acquisition condition and a result filtering condition based at least in part on the business elements.