m4_comment([$Id: db_deadlock.so,v 10.32 2006/10/05 01:06:08 bostic Exp $])

include(m4/m4.utility)
define(M4PAGELOCAL, db_deadlock)

m4_util_header(db_deadlock, [dnl
db_deadlock m4_utilarg(Vv)
    m4_utilarg([a e | m | n | o | W | w | y]) m4_utilarg([h home]) m4_utilarg([L file]) m4_utilarg([t sec.usec])])
m4_idefz(utility to detect @deadlocks)

m4_p([dnl
The m4_ref(db_deadlock) utility traverses the database environment lock
region, and aborts a lock request each time it detects a deadlock or a
lock request that has timed out.  By default, in the case of a deadlock,
a random lock request is chosen to be aborted.])

m4_p([dnl
This utility should be run as a background daemon, or the underlying
m4_db deadlock detection interfaces should be called in some other way,
whenever there are multiple threads or processes accessing a database
and at least one of them is modifying it.])

m4_p([The options are as follows:])

m4_tagbegin
m4_tagopt(a, [dnl
When a deadlock is detected, abort the locker:
m4_tagbegin
m4_tag(m, [with the most locks])
m4_tagns(n, [with the fewest locks])
m4_tagns(o, [with the oldest lock])
m4_tagns(W, [with the most write locks])
m4_tagns(w, [with the fewest write locks])
m4_tagns(y, [with the youngest lock])
m4_tagend])
m4_p([dnl
When lock or transaction timeouts have been specified:
m4_tagbegin
m4_tag(e, [abort any lock request that has timed out])
m4_tagend])

m4_hflag

m4_Lflag(db_deadlock)

m4_tagopt(t, [dnl
Check the database environment every m4_arg(sec) seconds plus
m4_arg(usec) microseconds to see if a process has been forced to wait
for a lock; if one has, review the database environment lock
structures.])

m4_Vflag

m4_tagopt(v, [dnl
Run in verbose mode, generating messages each time the detector runs.])

m4_tagend

m4_p([dnl
If the m4_option(t) option is not specified, m4_ref(db_deadlock) will
run once and exit.])

m4_detach(db_deadlock, uses)

m4_p([dnl
The m4_ref(db_deadlock) utility does not attempt to create the m4_db
shared memory regions if they do not already exist.  The application
which creates the region should be started first, and then, once the
region is created, the m4_ref(db_deadlock) utility should be started.])

m4_underfunc(lock_detect, lock_detect, db_deadlock)

m4_utilexit(db_deadlock)

m4_header([Environment Variables])

m4_utilenv(db_deadlock)

m4_page_footer