[Koha] safe way

i rebuild zebra with - b - a - ( OK ) and when running with - z manually didn't make any thing -- why ?? that's my crontab # m h dom mon dow command PERL5LIB=/usr/share/koha/lib/ KOHA_CONF=/etc/koha/koha-conf.xml ## rebuild zebra */5 * * * * KOHA_CONF=/etc/koha/koha-conf.xml PERL5LIB=/usr/share/koha/lib/ /usr/share/koha/bin/migration_tools/rebuild_zebra.pl -b -a -z >/dev/null all my worry about we are thinking to make consortium between a few libraries and i'm afraid of this point indexing so i asking if there anther solution for indexing .....because i'm sure there are another way to make koha indexing .... without crontab .... that's right or not .... thank's