You meet following problems in your system.
1) Tables ACCTHD, ACCTIT & ACCTCR grow significantly even you update statistics.
2) After the archiving and the tables reorganization still there is no change for the size of tables.
3) EWA report shows recommendation about ACCTIT Table Reorganization.
The ACCT** tables store document information for postings from material management. So on every MM invoice or goods movement posting a document will be stored in the ACCT** tables. This document is basically a copy of the document information sent from MM to accounting.
The information stored in tables ACCTHD, ACCTIT and ACCTCR are only available during the runtime of document processing for postings from MM.
So if you post large invoices or goods movement documents frequently, the number of records in ACCT** tables will increase accordingly.
First, SAP Best Practices recommend that you archive Accounting Interface documents (MM) entries after 6 months, since they probably no longer need to be accessed frequently after this period of time.
Second, archive the content of database tables ACCTHD, ACCTIT and ACCTCR using the archiving object MM_ACCTIT either in transaction SARA
Third, If you do not use subsequentdocument update in special ledger, profit center accounting, CO or funds management and do not need the content of tables ACCTHD, ACCTIT and ACCTCR you can also deactivate the update of those tables completely.
Fourth, from technical point of view, it is no problem to delete the ACCT* table entries. Of course you can archive them before deleting, in case you want to restore those information.
For more information, please check SAP notes 48009 and 83076 and following KBAs.