Unavailability of Data Source

Hi Community,

We have 10 register in our store, register 1 which is the lead register (store primary) and register 2,3,4... are  the non-lead register. In non lead registers out of all register one register transaction getting failed to persist to DB.

Error :-  Data Source Unavailable.

For this I have some questions

1) How come one register is coming Unavailable Database out off all Register ?

2) If one register DB going offline it should go all register's DB also offline right because all registers are pointing to one DB  i.e. Store primary (Lead)?

Due to above problem TRN_TRANS Table contain the transaction information but TRN_POSLOG_DATA is missing.