Diagnosing Multipath IO Timeout

Multipath, SAN, SCSI … etc. might be the most widely used technology and terms in our industry. Nevertheless, missing details would frequently lead to difficulties in explaining curious problems. For instance, our storage admin migrated old SAN switch to newer ones recently. The procedure would roughly include unplugging and plugging of Fibre Channel lines, which… Continue reading Diagnosing Multipath IO Timeout

Analyzing accesslog with awk and sed

— top 10 URL sed -n ‘/2018:07:30/,/2018:09:30/ p’ localhost_access_log.`date +%Y-%m-%d`.txt | \ awk ‘{print $9}’ | sed -r ‘s#(.*)[?$](.*)#\1#’ | sort | uniq -c | sort -k1n | tail -10 — top 10 IP addr sed -n ‘/2018:13:30/,/2018:14:30/ p’ localhost_access_log.`date +%Y-%m-%d`.txt | \ grep “cm-s-notice-query/draftInfo” | awk ‘{print $(NF-1)}’ | sort | uniq -c |… Continue reading Analyzing accesslog with awk and sed

pcap file format

https://wiki.wireshark.org/Development/LibpcapFileFormat Libpcap File Format magic_number: used to detect the file format itself and the byte ordering. The writing application writes 0xa1b2c3d4 with it’s native byte ordering format into this field. The reading application will read either 0xa1b2c3d4 (identical) or 0xd4c3b2a1 (swapped). If the reading application reads the swapped 0xd4c3b2a1 value, it knows that all the… Continue reading pcap file format

NAT Traversal Practices for Client-Server SIP

https://tools.ietf.org/html/rfc6314 NAT Traversal Practices for Client-Server SIP ALGs have limitations (as per RFC 4787 [RFC4787] Section 7, RFC 3424 [RFC3424], and [RFC5245] Section 18.6), and experience shows they can have an adverse impact on the functionality of SIP. This includes problems such as requiring the media and signaling to traverse the same device and not… Continue reading NAT Traversal Practices for Client-Server SIP

MySQL connect to unexpected instance

This morning, I ran into this strange problem: Linux user root cannot connect to local MySQL instance while user mysql can. However, it seems that it connected to the wrong instance. [root@SMNYDBS06 ~]# mysql -h localhost -u root –port=3307 ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock’ (111) [root@SMNYDBS06 ~]# su… Continue reading MySQL connect to unexpected instance

Cross-platform data replication

11G – Reduce Transportable Tablespace Downtime using Cross Platform Incremental Backup (Doc ID 1389592.1) RMAN DUPLICATE/RESTORE/RECOVER Mixed Platform Support (Doc ID 1079563.1) Data Guard Support for Heterogeneous Primary and Physical Standbys in Same Data Guard Configuration (Doc ID 413484.1)

Step-by-step guide on installing and configuring OGG for Oracle replication(Part III – Monitoring and High Availability)

# create heartbeat job on source database exec dbms_scheduler.drop_job(job_name=>’OGG_HEARTBEAT_JOB’); create table nlnk.test(id number); BEGIN DBMS_SCHEDULER.create_job ( job_name => ‘ogg_heartbeat_job’, job_type => ‘PLSQL_BLOCK’, job_action => ‘BEGIN insert into nlnk.test(id) values(to_number(to_char(sysdate,”yyyymmddhh24miss”))); END;’, start_date => systimestamp, end_date => NULL, repeat_interval => ‘freq=minutely;bysecond=0;interval=1′, enabled => true); END; / exec dbms_scheduler.run_job(job_name=>’OGG_HEARTBEAT_JOB’); col max(id) for 99999999999999 select max(id) from NLNK.test; alter… Continue reading Step-by-step guide on installing and configuring OGG for Oracle replication(Part III – Monitoring and High Availability)