The Flashback Buffer Wait alarm indicates that the percentage of available time spent waiting for the Recovery Writer (RVWR) to write data to the flashback logs has exceeded a specified threshold.
Normally, sessions do not need to wait for flashback entries to be written. However, if new blocks are added to the buffer cache faster than the Recovery Writer (RVWR) can write them to the flashback recovery area, sessions may wait for the RVWR to write its buffers to disk before they can modify or add new buffers.
Most RVWR waits occur because the flash recovery area is on a volume that has insufficient bandwidth (for example, too few disk spindles) to cope with the load. A typical solution is to place the flashback area on a striped volume that has a greater number of disk devices. In general, you should place the flashback recovery area on a stripe that is at least as wide as the stripe containing database files.
Alleviate short-term bottlenecks by increasing the size of the buffer cache.