You may enable multiple levels by specifying the debug option once for each desired level. Or, since debugging levels are additive, you can do the math yourself. That is, if you want to trace function calls and watch the config file being processed, you could set level to the sum of those two levels (in this case, {{EX: -d 65}}). Or, you can let slapd do the math, (e.g. {{EX: -d 1 -d 64}}). Consult {{F: <ldap_log.h>}} for more details.
Note: slapd must have been compiled with {{EX:-DLDAP_DEBUG}}
Note: slapd must have been compiled with {{EX:--enable-debug}}
defined for any debugging information beyond the two stats levels