Save the DB in background.
Normally the OK code is immediately returned. Redis forks, the parent continues to serve the clients, the child saves the DB on disk then exits.
An error is returned if there is already a background save running or if there is another non-background-save process running, specifically an in-progress AOF rewrite.
If BGSAVE SCHEDULE is used, the command will immediately return OK when an
AOF rewrite is in progress and schedule the background save to run at the next
opportunity.
A client may be able to check if the operation succeeded using the LASTSAVE command.
Please refer to the persistence documentation for detailed information.
*Return value
Simple string reply: Background saving started if BGSAVE started correctly or Background saving scheduled when used with the SCHEDULE subcommand.
*History
>= 3.2.2: Added theSCHEDULEoption.