If you have enabled HADR between 2 databases, the following value of parameters might give you better performance.
Database configuration parameters
LOGFILSIZ = 6000 LOGBUFSZ = 512 SOFTMAX = 125
DB2 Registry variables
db2set DB2TCP_CLIENT_RCVTIMEOUT=20 db2set DB2_HADR_BUF_SIZE=10240
If you are still not getting the performance that you were getting without HADR, you may start manipulating value of LOGBUFSZ. Please remember that replication in peer-to-peer stage happens at log buffer level so LOGBUFSZ and DB2_HADR_BUF_SIZE should be adjusted accordingly.
If you have high performance INSERTS going on, you should increase the value of LOGBUFSZ.