OpenLDAP: ldap clients cannot find entries because of database corruption

Issue

• The ldap clients like ldapsearch command cannot find entries.
• The following error messages happen in the slapd/ldap log file.

Jan 25 12:05:24 exampledb slapd[8219]: bdb(): PANIC: fatal region error detected; run recovery 
Jan 25 12:05:24 exampledb slapd[8219]: bdb_db_close: close failed: DB_RUNRECOVERY: Fatal error, run database recovery (-30974) 

Feb  8 16:33:24 exampledb slapd[11088]: bdb(): page 0: illegal page type or format
Feb  8 16:33:24 exampledb slapd[11088]: bdb(): PANIC: Invalid argument
Feb  8 16:33:24 exampledb slapd[11088]: bdb(): PANIC: fatal region error detected; run recovery

• slapd_db_recover command fixes the errors temporarily. The problem happens again after a while. How should we fix the corruption?