Dump/snapshot problems

[Eugene]

Hi people,

Sometimes I have strange problems with dump -- or, rather, with snapshot it
makes.
System is FreeBSD 5.3, default kernel configuration

Two types of problems:
1) System hangs or at least not accessible over the network and has to be
physically reset. Last message on console
Collecting pv entries -- suggest increasing PMAP_SHPGPERPROС
maxproc limit exceeded by id(0), please see tuning(7) and login.conf(5)

Question: what exactly should I tune?

2) Dump process dies with message
mksnap_ffs: Cannot create //.snap/dump_snapshot: Resource temporarily
unavailable
dump: Cannot create //.snap/dump_snapshot: No such file or directory

dmesg message
fsync: giving up on dirty: 0xc57b5d68: tag devfs, type VCHR, usecount 60263,
writecount 0, refcount 960, flags (VV_OBJBUF), lock type devfs: EXCL
(count 1) by thread 0xc610f7d0 (pid 87575)
dev ad4s1a

What is wrong?  What is '0xc57b5d68' (number is repeating)?

Thanks in advance
Eugene