Resuming an ArcSDE service using sdemon
Use the sdemon command with the resume operation to restart a remote ArcSDE service from a UNIX, Linux, or Windows server or a local ArcSDE service on UNIX or Linux.
When the service is paused, neither ArcSDE service nor direct connections can be made to the geodatabase until the service is resumed.

Windows users must have power user or administrator group permissions to pause, resume, or shut down a local or remote ArcSDE service.
Steps:
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At an MS-DOS command prompt (Windows) or shell prompt (UNIX or Linux), type the sdemon command with the resume operation.
sdemon –o resume –p nevermind –s squirrel –i 6543 ArcSDE I/O Manager is Resuming, new connections will now be allowed
8/25/2014