meaning of service_update in listener.log

Hello,

Could you please advise the meaning of service_update in llistener.log?

<txt>11-APR-2014 11:02:50 * (CONNECT_DATA=(CID=(PROGRAM=JDBC Thin Client)(HOST=__jdbc__)(USER=zladmin))(SERVICE_NAME=zlprodeu.world)(CID=(PROGRAM=JDBC Thin Client)(HOS

T=__jdbc__)(USER=zladmin))) * (ADDRESS=(PROTOCOL=tcp)(HOST=xxx.yyy.171.98)(PORT=41618)) * establish * zlprodeu.world * 0

</txt>

</msg>

<msg time='2014-04-11T11:02:53.710+02:00' org_id='oracle' comp_id='tnslsnr'

type='UNKNOWN' level='16' host_id='eudc-oragrid-ux01'

host_addr='xxx.yyy.158.44'>

<txt>11-APR-2014 11:02:53 * service_update * zlprodeu_01 * 0

</txt>

</msg>

<msg time='2014-04-11T11:03:05.715+02:00' org_id='oracle' comp_id='tnslsnr'

type='UNKNOWN' level='16' host_id='eudc-oragrid-ux01'