You can mark a library offline for maintenance to perform administrative or maintenance tasks on the library
When this option is enabled, the library is unavailable for read/write operations such as backup, restore or auxiliary copy operations. However, the library will be available to perform other administrative tasks.
Procedure
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From the CommCell Browser, expand Storage Resources | Libraries. 
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Right-click the appropriate library, click Properties and then click Mark Library Offline for Maintenance. 
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Click OK. 
Result
The library will be marked offline for maintenance.