oldWals are supposed to be cleaned in master background chore, I also doubt they are needed.

HBASE-20352(for 1.x version) is to speed up cleaning oldWals, it may address your concern "OldWals is quite huge"

From: Manjeet Singh <[EMAIL PROTECTED]>
Sent: 12 July 2018 08:19:21
Subject: Re: Query for OldWals and use of WAl for Hbase indexer

I have one more question

If solr is having its own data mean its maintaining data in their shards
and hbase is maintaining in data folder... Why still oldWals need?

Manjeet singh

On Wed, 11 Jul 2018, 23:19 Manjeet Singh, <[EMAIL PROTECTED]>