Troubleshooting and practical guidance
Record the exact message, product version, target computer, selected drive, method, and time of the problem. Use reports and Windows event entries to distinguish a failed action from one that was skipped or paused.
Connection refused or error 10061
Check that the O&O Defrag service is running, then inspect its events and connection settings. Classic components use TCP port 50300; local or remote firewall restrictions can block communication. Keep the firewall enabled and review the appropriate rule. See Network management.
A task did not run
Check that it is enabled, within its date range, and has eligible drives and methods. Review the fragmentation threshold, missed-run setting, maximum runtime, AC-power rule, and program/CPU/drive-load guards. A screensaver task depends on screensaver activity. A task configured for standby wake cannot run while the computer is fully powered off.
Also inspect the tray's hibernation mode, drive availability, pre-task command failures, and any warning from the file-system pre-check. Saved tasks can differ from global settings.
Files remain fragmented or a run takes too long
Review file locks, exclusions, the size threshold, free working space, the chosen method, and competing file activity. An initial full sorting pass can take much longer than subsequent maintenance. Check ClusterInspector and File status before repeating a full-drive operation.
Check available working space, the size of the largest files, and contiguous free regions. See Free working space. Use the supported restart-based maintenance environment only when appropriate for eligible locked files.
Drive errors, SSD writes, and health warnings
The integrated Check drive and pre-defragmentation check are read-only. They detect file-system problems without repairing them. Preserve important data and investigate errors before further optimization.
SOLID file optimization can increase short-term writes, particularly for complete passes. TRIM is a separate operation. Logical file extents do not reveal the SSD controller's physical flash placement, and neither a low fragmentation percentage nor a good S.M.A.R.T. rating guarantees hardware life or data safety.
Shadow copies and restore points
Moving data can increase copy-on-write storage use on systems using shadow copies. Check free space and snapshot retention when planning a large rearrangement. Do not disable System Protection as a routine preparation step: doing so can remove existing restore points. Coordinate maintenance with the backup and snapshot policy for that system.
Choose suitable maintenance windows
For a home or office PC, automatic maintenance with resource limits can reduce manual work. For gaming or recording sessions, use ActivityMonitor's program list or run deliberate maintenance outside the session. For heavily used servers, schedule work around backups and other disk activity. Notebook users can enable AC-only operation and pause-on-battery.
Optimization is designed to preserve file contents, attributes, and permissions during normal operation. It does not replace a backup or make interruptions harmless. Avoid copying, moving, or deleting large amounts of data during maintenance when possible.
Get help
Contact O&O Software support with the exact version and edition, interface, drive type, steps to reproduce, and relevant reports. Remove license keys and unnecessary personal file paths from material shared publicly. If a procedure's labels do not match your window, return to Choose your interface.