Transaction Events database, Index optimization task and the disk requirement to prevent data corruption.
Transaction Events database (traces.db) requires additional memory for optimization tasks. In addition to the CPU requirement, the Transaction Event database (traces.db) periodically requires additional free disk space in order to perform optimization tasks. This disk usage is transient, temporary and requires approximately twice the current size of the traces.db file. Failure to provide adequate free disk space can result in poor traces database performance or Transaction Trace data corruption.
For instance, if you have 8 GB of trace indexing, you need a minimum of 16 GB of HD space. This is because lucene needs to allocate an amount equal to the current index size when it is doing index compaction. For more details, refer to the below link: http://lucene.apache.org/java/2_9_1/api/all/org/apache/lucene/index/IndexWriter.html; see Optimize section.