2749124 - sp_iqcheckdb allocation hang -- SAP IQ

On Simplex IQ server 'sp_iqcheckdb allocation' appeared  hang.

Previously, dbspace size = 11.5Tb, 96% full.
and there was errors: "You have run out of space in PRADA_MAIN DBSpace".
The developers are convinced that there are no more than 100Gb data + transaction versions generated.
Nonetheless, 1 more Tb is added and there is no more error.

But customer wants to know if there could be fragmentation, block leaks.
But when running sp_iqcheckdb 'allocation dbspace XXXX' , after one hour, no more DBCC progression message is printed.
They tried running DBCC twice.
The first time, DBCC was still running after 11 hours, it seems the DBCC connection could be dropped.
The 2nd time DBCC was still running, after 17 hours, DBCC connection could not be dropped.
Eventually, IQ had to be killed and restarted to get rid of this DBCC connection.
For the 2 DBCC runs, DBCC stops printing DBCC messages after 1 hour.

To know why DBCC is stucked, they would need to run DBCC again and collect pstacks, but then,
there is a risk that DBCC runs forever and connection cannot be dropped unless IQ is killed

SAP IQ 16.1

unresponsive, hang, stuck, CR816301, 816301, , KBA , BC-SYB-IQ , Sybase IQ , Problem