TrimA feature of the Data Set management command available in the ATA8-ACS-2 specification. The command is used in the operating system used to wipe invalid data blocks on solid-state drives (SSD) which are no longer in use - including data blocks which have been left by deleted files.
Traditionally, flash media could not overwrite existing data as it first would need to first perform a 512KB block erase. Overwriting data on a SSD, required a longer read-modify-write operation which decreased the performance and speed of the SSD. The Trim command enables file system information to be collected by the OS and sends it to the SSD controller, which otherwise would not know it could delete those blocks.
The purpose of Trim is to improve the speed of SSD drives and ultimately boost the drives' overall read and write performance. Both the operating system and SSD firmware must support Trim. Trim may also be referred to as DisableDeleteNotify, or SSD Optimizer.