So I found an issue in my syslog like the below. I edited the /etc/zabbix/zabbix_server.conf file and changed CacheSize=8M to CacheSize=16M.
Jul 22 20:27:35 knowledge zabbix_server[2778]: Starting Zabbix Server. Zabbix 4.4.10 (revision 4db30afc70). Jul 22 20:27:35 knowledge zabbix_server[2778]: ****** Enabled features ****** Jul 22 20:27:35 knowledge zabbix_server[2778]: SNMP monitoring: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: IPMI monitoring: YES Jul 22 20:27:35 knowledge systemd[1]: Started Zabbix Server. Jul 22 20:27:35 knowledge zabbix_server[2778]: Web monitoring: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: VMware monitoring: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: SMTP authentication: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: ODBC: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: SSH support: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: IPv6 support: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: TLS support: YES Jul 22 20:27:35 knowledge zabbix_server[2778]: ****************************** Jul 22 20:27:35 knowledge zabbix_server[2778]: using configuration file: /etc/zabbix/zabbix_server.conf Jul 22 20:27:35 knowledge zabbix_server[2778]: current database version (mandatory/optional): 04040000/04040002 Jul 22 20:27:35 knowledge zabbix_server[2778]: required mandatory version: 04040000 Jul 22 20:27:35 knowledge zabbix_server[2778]: server #0 started [main process] Jul 22 20:27:35 knowledge zabbix_server[2784]: server #1 started [configuration syncer #1] Jul 22 20:27:35 knowledge zabbix_server[2784]: __mem_malloc: skipped 0 asked 24 skip_min 18446744073709551615 skip_max 0 Jul 22 20:27:35 knowledge zabbix_server[2784]: [file:dbconfig.c,line:94] __zbx_mem_realloc(): out of memory (requested 24 bytes) Jul 22 20:27:35 knowledge zabbix_server[2784]: [file:dbconfig.c,line:94] __zbx_mem_realloc(): please increase CacheSize configuration parameter Jul 22 20:27:35 knowledge zabbix_server[2784]: === memory statistics for configuration cache === Jul 22 20:27:35 knowledge zabbix_server[2784]: min chunk size: 18446744073709551615 bytes Jul 22 20:27:35 knowledge zabbix_server[2784]: max chunk size: 0 bytes Jul 22 20:27:35 knowledge zabbix_server[2784]: memory of total size 8388232 bytes fragmented into 70489 chunks Jul 22 20:27:35 knowledge zabbix_server[2784]: of those, 0 bytes are in 0 free chunks Jul 22 20:27:35 knowledge zabbix_server[2784]: of those, 7260424 bytes are in 70489 used chunks Jul 22 20:27:35 knowledge zabbix_server[2784]: ================================ Jul 22 20:27:35 knowledge zabbix_server[2784]: === Backtrace: === Jul 22 20:27:35 knowledge zabbix_server[2784]: 11: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](zbx_backtrace+0x4e) [0x55803bd6662b] Jul 22 20:27:35 knowledge zabbix_server[2784]: 10: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](__zbx_mem_realloc+0x160) [0x55803bd619af] Jul 22 20:27:35 knowledge zabbix_server[2784]: 9: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](+0x18c453) [0x55803bd27453] Jul 22 20:27:35 knowledge zabbix_server[2784]: 8: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](+0x19889b) [0x55803bd3389b] Jul 22 20:27:35 knowledge zabbix_server[2784]: 7: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](DCsync_configuration+0x12d7) [0x55803bd34de6] Jul 22 20:27:35 knowledge zabbix_server[2784]: 6: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](dbconfig_thread+0x116) [0x55803bbeb021] Jul 22 20:27:35 knowledge zabbix_server[2784]: 5: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](zbx_thread_start+0x37) [0x55803bd74862] Jul 22 20:27:35 knowledge zabbix_server[2784]: 4: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](MAIN_ZABBIX_ENTRY+0x996) [0x55803bbdca4e] Jul 22 20:27:35 knowledge zabbix_server[2784]: 3: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](daemon_start+0x2ff) [0x55803bd65d8c] Jul 22 20:27:35 knowledge zabbix_server[2784]: 2: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](main+0x305) [0x55803bbdc0a2] Jul 22 20:27:35 knowledge zabbix_server[2784]: 1: /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7) [0x7fd8e5ea1b97] Jul 22 20:27:35 knowledge zabbix_server[2784]: 0: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](_start+0x2a) [0x55803bbdb11a] Jul 22 20:27:35 knowledge zabbix_server[2778]: One child process died (PID:2784,exitcode/signal:1). Exiting ... Jul 22 20:27:35 knowledge zabbix_server[2778]: syncing trend data... Jul 22 20:27:35 knowledge zabbix_server[2778]: syncing trend data done Jul 22 20:27:35 knowledge zabbix_server[2778]: Zabbix Server stopped. Zabbix 4.4.10 (revision 4db30afc70).