Not All Endpoints Registered

If issuing “crsctl status resource” command show the status of listener as “Not All Endpoints Registered”, it is usually because of contradictions in the Listener settings. It means that probably you have a manually setup listener (by editing listener.ora file) with different settings than registered with the CRS/HAS. Or, there could be multiple listeners configured from multiple oracle homes – one from Grid Infrastructure home, and other listener with same configuration running from other home and started manually (using lsnrctl command).

DBMS_AW_EXP: BIN$ZRGxDTT9TumIWFOmM0qIHQ==$0 not AW$

If you see any similar messages during expdp, you may ignore these messages. Alternatively, you may purge the recyclebin and initiate the expdp again. Issue “purge dba_recyclebin” from SQLPUS. The messages displayed in expdp log are as follows.

Initialization parameter setting back to original value

I faced a very strange situation whereby I was setting my log_archive_dest_1 parameter using ALTER SYSTEM command with SCOPE=BOTH, which meant that this parameter value change should have been consistent across the instances reboot as this change was also being made in the spfile (SPFILE was in use for that database/instance) as well as in memory. However, it was not happening actually. After every instance restart, the value of this parameter would again set to the old value and this was causing problems for us.

ORA-00972: identifier is too long

In Oracle 12.1 and below, the maximum length for the name of an object (Table, View, Procedure, Package, Function, Materialized View etc.) is 30 bytes (or 30 characters, if each character is of 1 byte as per character set used). Starting 12.2, name length has been increased to 128 bytes/characters. Likewise, the name of a column of a table or view should also not exceed the allowed length. In the following I am providing a few examples where we will see ORA-00972 error returned in 12.1 database

SQL Plan Management and SQL Baseline

Before you read this article, I would suggest you to read my articles about bind variable peeking and adaptive cursor sharing.

Starting 11g release, adaptive cursor sharing makes optimizer to generate and select multiple execution plans based on the bind variable values passed during the execution. Oracle also introduced SQL Plan Management feature starting 11g whereby the history of plans of an SQL is maintained in SQL Baseline and out of which one or more plans can become “accepted” and can be used for that SQL. This is our choice to make plan(s) “accepted” if think that plan is optimal. We may ignore sub-optimal plans. In this will explain SQL Plan Management using an example.

gc buffer busy acquire and gc buffer busy release

These two wait events are similar to ”buffer busy wait” that you might have observed which is recorded when a session tries to access a data block/buffer which is already being accessed by another session that is connected to the same instance and buffer is also in the current instance’s buffer cache. In RAC environment, if a session tries to read a buffer from a remote instance’s buffer cache but the buffer is already being read by a different session, a “gc buffer busy acquire” wait event is recorded. If a session tries to read a buffer from the buffer cache of local instance, but buffer is already being read into remote instance’s buffer cache from local cache by a session connected to that remote instance, a “gc buffer busy release” wait event is recorded.  

ORA-15046: ASM file name...is not in single-file creation form

We can use ASM provided command “cp” to copy files from file system to ASM diskgroup and vice versa; and also from one ASM diskgroup to the other. If you receive ORA-15046 while copying a file to an ASM diskgroup from file system, or from another diskgroup, mostly it is because you are providing a file name for the destination file that is not allowed in the ASM. From file name here I mean the file name in the format that is used in ASM i.e. file_name.235.84753829. Same error would also come if an invalid directory location is provided. Following is an example of this error message

DBA_TABLESPACE_USAGE_METRICS and CDB_TABLES_ACES_USAGE_METRICS

DBA_TABLESPACE_USAGE_METRICS and CDB_TABLESPACE_USAGE_METRICS (starting 12c) provide us summary of space usage of each tablespace including TEMP and UNDO tablespaces. Only different between these 2 views is same as between all other CDB* and DBA* views whereby CDB* views contain information from all PDBs that is viewable from root container and have an extra column CON_ID to correspond each row to a particular PDB. Using this view makes it very easy to analyze space usage. In this article I would explain how to get information from these dictionary views to check the utilization of space within the tablespace(s). You may also want to read my articles about Tablespace space usage history and forecast for 12c and above, and for 11g and 10g.

Adaptive Cursor Sharing

This feature was introduced in 11g release 1 to cater a performance issue caused by bind variable peeking. Adaptive cursor sharing means that if an SQL is submitted for execution that has bind variables, and it already has an execution plan in shared pool, still optimizer can generate a new execution plan based on the values passed in the bind variable this time. This means that on every call of an SQL, optimizer may use already available plans in the shared pool, or it may generate a new one that is more efficient based on the bind variable values.

Bind Variable Peeking Prior to 11g

Oracle has a feature called “bind variable peeking” whereby an execution plan for an SQL is generated based on the bind variable values used in the SQL. This technique sometimes created suboptimal execution plan because the plan might be perfect for the SQL containing bind variables based on which this plan was generated, but if same SQL is executed later with different values in bind variables, this current plan may not be optimal for those values, and might cause performance degradation for the SQL. I have discusses a real scenario in this article.