Search notes:

Oracle: DBMS_LOCK_ALLOCATED

dbms_lock_allocated is a table that is populated when a locks are requested using dbms_lock.allocate_unique or dbms_locak.allocate_unique_autonomous. 
select
   lck.type               lock_type,
   dla.name,
   lck.lmode,
   lck.request,
   round(lck.ctime / 100) tim,
   lck.block,
   dla.lockid,
   lck.sid,
   round(dla.expiration - sysdate, 1) exp_in_days
from
   dbms_lock_allocated dla   left join
   gv$lock             lck on dla.lockid = lck.id1;

Cleaning up

Records where expiration is less than sysdate are deleted by dbms_lock.allocate_unique or dbms_locak.allocate_unique_autonomous on every 100th attempt to create a new entry.

See also

MOS Note 840840.1

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:51 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(51): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(66): id_of(Object(PDO), 'uri', '/notes/developm...') #2 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/developm...', 1788444495, '216.73.217.21', 'Mozilla/5.0 App...', NULL) #3 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/development/databases/Oracle/installed/packages/dbms/lock/dbms_lock_allocated(56): insert_webrequest() #4 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 51