Despite the fact that there were some speculations that Oracle Database 12c will be released on 12.12.(20)12 to use the Magic of 3×12, this opportunity was missed by Oracle and Release 12c is still in Beta Testing period,
so we have to wait for the another ‘good’ moment like 3×13(12.13.13) 😉
Later we’ll see if it add more power to new Release… 😉
I have been contacted by one of our customers to provide reference information on troubleshooting Oracle Log File Sync waits.
I think that this information worth short blog post.
- Log File Sync waits occur when sessions wait for redo data to be written to disk
- typically this is caused by slow writes(IO subsystem saturation,…)
- spikes in Log File Parallel Write, as shown by James Morle
- or the application is committing too frequently
- improper Operating System configuration(check 169706.1)
- CPU overburning(very high demand => LGWR on run queue, check Kevin Closson post)
- high Log Parallelism, which saturates filesystem/OS, as investigated by Nikolay Savvinov
- BUGs in Oracle(especially with RAC option) and 3rd Party software(like ODM/DISM)
Recently I was involved in performance troubleshooting of one quite expensive system
that had performance problems during business hours.
I’ll not provide all details, but just post some pictures that will show resource usage:
Oracle memory allocation:
Linux memory allocation
or from other side:
MemTotal: 98848220 kB
MemFree: 75109972 kB
Buffers: 597460 kB
I was doing RMAN RESTORE database for refreshing developers’ stand and stuck on next situation:
SET UNTIL SCN 18508482749;
SET NEWNAME FOR DATABASE TO ‘/oradata1/oradata/XXX/%b’;
creating datafile file number=1 name=/oradata1/oradata/XXX/system01.dbf
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-03002: failure of restore command at 08/08/2012 13:27:26
ORA-01180: can not create datafile 1
ORA-01110: data file 1: ‘/oradata1/oradata/XXX/system01.dbf’ Continue reading
Recently I have published post about issue with RMAN duplication of Oracle database when standby database was used as a target. Later in updates of mentioned post I have confirmed that with fix for BUG:11715084 everything works as expected.
Today I have decided to make post with step-by-step procedure with which I have tested mentioned feature – making standby database from standby database.
I will Simplify setup As Much As Possible(SAMAP):
- single machine will be used as a host for all 3 databases
- OMF(Oracle Managed Files) will be used for managing files location and file names
- FRA(Fast/Flash Recovery Area) will be used for archive logs
Today I was contacted by one of our customers (one of the biggest Ukraine banks) – that faced next issue after upgrading server-size PL/SQL code to new version on one of their critical systems:
- they wasn’t able to compile one of packages – package compilation session just ended with the next message
- ORA-01331 end of file communication channel
- from the server-side(trace-file) error message was next:
- ORA-07445: exception encountered: core dump [opixrb()+6944] [SIGSEGV] [ADDR:0x0] [PC:0x103C1D980] [Address not mapped to object] 
- current SQL Statement from the trace-file:
- SELECT :”SYS_B_0″ DUMMY FROM “dbo”.”sysusers”@APS WHERE “name” = :”SYS_B_1″
- customer confirmed that they are using Oracle Gateway (Heterogeneous Services) link to Microsoft SQL Server inside mentioned package
- there weren’t any changes to mentioned package during application code update
- there weren’t any patches applied to ORACLE_HOME since everything worked OK
- it just stopped compiling
- they must have working system tomorrow morning! Continue reading
Just after every installation of OEM Grid Control/Database Control and while accessing Console you will see next message:
There is a problem with this website’s security certificate.
The security certificate presented by this website was not issued by a trusted certificate authority.
Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.
We recommend that you close this webpage and do not continue to this website.
Click here to close this webpage.
Continue to this website (not recommended).
It’s much better to sign OMS with certificate issued by Trusted Third-Party Certificate Authority(see References section below), but it’s not always possible, so I will provide step-by-step instruction with screenshots how to fix this ussue locally on your desktop’s browser. Continue reading