ORA-600 [ossnet_assign_msgid_1] on Exadata

On a Exadata system with Oracle v12.1, a MERGE statement with parallelism was frequently failing with below ORA errors:

                   ORA-12805: parallel query server died unexpectedly
        ORA-06512

A quick look in the alert.log, an ORA-600 is noticed.

ORA-00600: internal error code, arguments: [ossnet_assign_msgid_1], [],[ ] 

The best and easy way to diagnose any ORA-600 errors is to utilize the ORA-600 tool available on MOS.

In our case, with large hash join, the following MOS note helped to fix the issue:

On Exadata Systems large hash joins can fail with ORA-600 [OSSNET_ASSIGN_MSGID_1] (Doc ID 2254344.1)

Cause:
On Exadata Systems large hash joins can fail with ORA-600 [OSSNET_ASSIGN_MSGID_1] and the root cause if often a too small default value  for _smm_auto_min_io_size  and  _smm_auto_max_io_size'

and the workaround to fix the issue is to set the following underscore (_) parameters:

_smm_auto_max_io_size = 2048
_smm_auto_min_io_size = 256

In some cases, the below MOS notes helps to fix ORA-600 [ossnet_assign_msgid_1] error.

ORA-600 [ossnet_assign_msgid_1] (Doc ID 1522389.1)
Bug 14512766 : ORA-600 [OSSNET_ASSIGN_MSGID_1] DURING RMAN CONVERSION