2680855 - Coordinator hangs after upgrade to SAP IQ 16 SP11 PL20 when drop partition is executed on secondary node

Coordinator hangs after upgrade to SAP IQ 16 SP11 PL20 when drop partition on large table is executed on secondary node.
Pstacks on hung coordinator show the thread executing Alter Partition is doing a Check Index Consistency which is running under forbid and until that is complete nothing else gets processed.

hos_pi_pread
hos_svbio::Read2
hos_mvbio::Read2
s_buf::ReadBufAndVerify
s_buf::Read
s_bufpartition::Find
s_blockmap::Find
s_pageListCursor::PositionPage
v2s_bmcontext::bmlfblkget
v2s_bmcontext::bmfndprvelt
s_bm::FindLastBit
s_bArray::CheckColumnEBMCoverageDBCC
hs_dp::CheckIndexConsistency
hs_dp::GetIdentity
db_IndexDef::FlushIndexIdentity
db_IndexDef::CloseSIndexWithLock
db_IndexDef::CloseSIndex
hdb_delete_indices::Cleanup
hdb_delete_indices::Delete_Indices
hdb_hdelete::Delete
db_alterpartition::Execute
st_command::DoCmdThroughResourceGate
db_iqddl::AlterPartition
UIQDDL_AlterPartition

Following conditions will cause the Coordinator hangs situation :

1. FP_NBIT_ENABLE_TOKENCOUNT_CHECK is enabled
2. Drop Partition for a large table (for e.g 20billion rows) is executed on Secondary node

The issue has not been seen in SAP IQ 16 SP11 PL13

• SAP IQ 16 SP11 PL20
• Linux x64

sybase ; multiple ; cn ; writer ; reader ; sp_iqcheckfpconsistency ; dbcc ; checkdb , KBA , BC-SYB-IQ , Sybase IQ , Bug Filed