Reindex data after extending retention

[ChristopherHolt]

Not sure the best way to go about this. We had an index that originally had a 30 day retention that they wanted extended to 1 year after it had been running for awhile. It was also originally setup to to collect new data going forward but they now also want all the historical data pulled into splunk as this was replacing a different tool. How do I restore the already retentioned data and collect the old data that was originally outside of the window of what we wanted pulled in? I've already adjusted the retention period and removed the ignoreolder=7d from the config. Am I just better off rebuilding the whole thing from scratch?

[monitor://<Path>]
index=<Appname>
sourcetype=chr
crcSalt = <SOURCE>

[<Appname>]
homePath = volume:hot/$_index_name
coldPath = volume:cold/$_index_name
summaryHomePath = volume:summaries/$_index_name
thawedPath = /opt/splunk/data/thawed/$_index_name
enableTsidxReduction = false
maxDataSize = auto_high_volume
frozenTimePeriodInSecs = 31536000

[isoutamo]

If those hosts didn’t contains any other data then just stop UF then remove …/var/lib/splunk/fishbucket (check spelling on your node) directory. Start UF service and it start to indexing everything from scratch. Then do this same for other nodes.

If those nodes contains also some other events what you cannot reindexing the you must remove those file by file and start reindexing only for those files. 
Here is one old post about it https://community.splunk.com/t5/Deployment-Architecture/Use-btprobe-reset-to-re-index-multiple-files...