# Limitations of TiDB Binlog

__*TiDB binlog limitations*__
__*A single column of integers*__
__*tidb_enable_async_commit*__
__*tidb_enable_1pc*__
__*tidb_enable_amend_pessimistic_txn*__

+ When TiDB Binlog is enabled, TiDB does not allow the creation of clustered indexes that are not a single integer column as the primary key
+ System variable tidb*enable*async_commit
+ TiDB system variable tidb*enable*1pc
+ TiDB system variable tidb*enable*amend*pessimistic*txn

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TiDB clustered index features: When TiDB Binlog is enabled, TiDB does not allow the creation of clustered indexes that are not a single integer column as the primary key; data insertion, deletion, and update actions of the created clustered index table are not synchronized downstream through the TiDB Binlog. To synchronize clustered index tables, upgrade to v5.1 version or use TiCDC.

TiDB system variable tidb*enable*async_commit: When TiDB Binlog is enabled, enabling this option does not improve performance. For improved performance, it is recommended to use TiDc instead of TiDB Binlog.

TiDB system variable tidb*enable*1pc: When TiDB Binlog is enabled, there is no performance improvement when this option is enabled. For improved performance, it is recommended to use TiDc instead of TiDB Binlog.

TiDB system variable tidb*enable*amend*pessimistic*txn: There is a compatibility issue between the two functions, and using them together will cause inconsistencies in the correctness of TiDB Binlog replication data.