Month: February 2021

RMAN may fail with error RMAN-10002: ORACLE error: ORA-00096: invalid value SIGNATURE for parameter remote_dependencies_mode, must be from among NO_OVERFETCH, OVERFETCH.

The error message is confusing here as remote_dependencies_mode can only take two values: TIMESTAMP or SIGNATURE. The suggested values may be anything else from another parameter.

When running RMAN command, it tries to do an “alter session set remote_dependencies_mode=signature” but fails to do so. This most probably indicates a parameter corruption in memory.

Check current value for remote_dependencies_mode

show parameter remote_dependencies_mode
NAME                                 TYPE        VALUE
------------------------------------ ----------- -----------
remote_dependencies_mode              string     TIMESTAMP

Try to change the value manually:

alter system set remote_dependencies_mode=signature;

If this is a parameter corruption issue, you will get the same error:

ORA-00096: invalid value SIGNATURE for parameter remote_dependencies_mode,must be from among NO_OVERFETCH, OVERFETCH.

In this case, the solution is to restart the database. This will fix the corruption and you will be able to run rman again.

When starting linux OS and that fsck fails with fsck.ext4: No such file or directory while trying to open /dev/mapper/myvg_mylv, usually the disks are mounted in read only mode.

To solve this issue, you’ll have cancel fsck and login to the console.

Remount / filestem as read only with mount -n -o remount,rw /

After that, you will be able to modify /etc/fstab and remove the entry that does not exists.

Reboot the OS and wait for fsck to finish.

If you get this error

ORA-27300: OS system dependent operation:sendmsg failed with status: 105
ORA-27301: OS failure message: No buffer space available
ORA-27302: failure occurred at: sskgxpsnd2

The solution is to:

1. Lower MTU to 16436. To do this, add following to /etc/sysconfig/network-scripts/ifcfg-lo or replace the value if MTU is already set in this configuration file.
   MTU=16436
2. Save the file, exit and restart the network service by running:
   systemctl restart network.service
3. Calculate the value for vm.min_free_kbytes to be 0.4 % of the total physical memory and multiply by the number of NUMA nodes.
   total=$(awk ‘/MemTotal:(.)/{print $2 }’ /proc/meminfo) numa_count=$(lscpu | awk ‘/^NUMA node(s)(.)/{print $3 }’)
   min_free_kb=$(expr $total / 250 * 1) # this is the
4. Increase the value of vm.min_free_kbytes accordingly. This can be done by adding following a new sysctl configuration.
   echo “vm.min_free_kbytes=$min_free_kb” > /etc/sysctl.d/99-vm_min_free_kbytes.conf

This will take the value of $min_free_kb from the previous step!

5. load the new values

sysctl –system

6. Verify the new value has been applied correctly.
   sysctl vm.min_free_kbytes