Message Oracle PGA-20945 - unable to log on to Oracle for transaction logging

ERROR	unable to log on to Oracle for transaction logging
CAUSE	The gateway server was unable to connect to the Oracle server where the transaction log table is stored. An Oracle server message will follow this message.
ACTION	Ensure that the Oracle server and its TNS listener are both operational. If the protocol is SNA: also check the PGA_LOG_DB, PGA_LOG_USER, and PGA_LOG_PASS parameters in the gateway init file and ensure that they specify the correct database string, userid, and password, respectively. If the protocol is TCP/IP: also check the PGA_TCP_DB, PGA_TCP_USER, and PGA_LOG_PASS parameters in the gateway init file and ensure that they specify the correct database string, userid, and password, respectively. Refer to the Oracle Server Messages and Codes Manual for information on the Oracle server message.