Processes and Threads in Linux

Linux /var/log/messages show the following info and the host hung: automount[4483]: expire_proc: expire thread create for /misc failed Why does a server crash with automount failing to create threads ? The issue is related to the maximum number of processes respectively the kernel parameter kernel.pid_max The following is the explanation of pid_max: /proc/sys/kernel/pid_max (since… Continue reading Processes and Threads in Linux

Suspicious slow I/O actually may not be an issue

OS: AIX 7.1 DB: Oracle single instance Multipath: MPIO LGWR trace file was complaining slow LGWR: *** 2016-08-05 22:08:21.187 Warning: log write elapsed time 103557ms, size 229KB *** 2016-08-05 22:09:49.053 Warning: log write elapsed time 87866ms, size 181KB bps is extremely low (smaller than 1M) although I/O utility has reached almost 100% iostat -D… Continue reading Suspicious slow I/O actually may not be an issue

Wait on Data file init write

Recently we encountered an odd problem. Many foreground sessions are waiting for background process w000 and w008. This background process coordinates the execution of various space management tasks, including proactive space allocation and space reclamation. SMCO dynamically spawns slave processes (Wnnn) to implement these tasks. top shows that the process status is D (uninterruptible sleep)… Continue reading Wait on Data file init write

Resolving inactive transaction branch

Recently we encountered wait event ‘invalid transaction branch’ and here is how we resolved it. OS: AIX 7.1 DB: Oracle RAC — identify session waiting for ‘invalid transaction branch’ select sid, serial#, program, machine, sql_id, status, WAIT_TIME_MICRO, event, seconds_in_wait from v$session where username=’ONL1′ and status=’ACTIVE’; 1551 35801 MasterMgmt@PRMBMTR01 (TNS V1-V3) PRMBMTR01 35y99s5k1rjh0 ACTIVE 113572… Continue reading Resolving inactive transaction branch