Using more UPS in cluster with one DB.
Midnight DB clean up cause deadlock and it is not possible to set up time for scheduler not to run at midnight.

scheduler is singleton per node ( https://github.com/aerogear/aerogear-unifiedpush-server/blob/master/service/src/main/java/org/jboss/aerogear/unifiedpush/service/metrics/DeleteOldPushMessageInformationScheduler.java )

Example: oracle DB ( FYI ... DB owner PUSHSRVAG ... DB application user APUSHSRVAG)
-----------------------------------------------------------------------------------------

• • • 2015-04-10 00:00:04.506
    • SESSION ID:(84.48937) 2015-04-10 00:00:04.506
    • CLIENT ID) 2015-04-10 00:00:04.506
    • SERVICE NAME:(SYS$USERS) 2015-04-10 00:00:04.506
    • MODULE NAME:(JDBC Thin Client) 2015-04-10 00:00:04.506
    • CLIENT DRIVER:(jdbcthin) 2015-04-10 00:00:04.506
    • ACTION NAME) 2015-04-10 00:00:04.506

• • • 2015-04-10 00:00:04.506
      DEADLOCK DETECTED ( ORA-00060 )
      See Note 60.1 at My Oracle Support for Troubleshooting ORA-60 Errors
      [Transaction Deadlock]

The following deadlock is not an ORACLE error. It is a
deadlock due to user error in the design of an application
or from issuing incorrect ad-hoc SQL. The following
information may aid in determining the deadlock:

Deadlock graph:
--------Blocker(s)------- --------Waiter(s)--------
Resource Name process session holds waits process session holds waits
TM-00013891-00000000-00000000-00000000 142 84 SX SSX 144 162 SX SSX
TM-00013891-00000000-00000000-00000000 144 162 SX SSX 142 84 SX SSX

Rows waited on:
Session 84: no row
Session 162: no row

----- Information for the OTHER waiting sessions -----
Session 162:
sid: 162 ser: 54036 audsid: 10790094 user: 115/APUSHSRVAG
flags: (0x41) USR/- flags_idl: (0x1) BSY/////-
flags2: (0x40009) //INC
pid: 144 O/S info: user: oracle, term: UNKNOWN, ospid: 11534420
image: oracle@s16000ks
client details:
O/S info: user: jbotp, term: unknown, ospid: 1234
machine: s1.sk.srv.acc.sys program: JDBC Thin Client
application name: JDBC Thin Client, hash value=2546894660
current SQL:
delete from PUSHSRVAG.PushMessageInformation where submitDate<:1

----- End of information for the OTHER waiting sessions -----

Information for THIS session:

----- Current SQL Statement for this session (sql_id=bsk109wpq55yg) -----
delete from PUSHSRVAG.PushMessageInformation where submitDate<:1