CONTAINERS clause and LONG columns

We were working on a monitoring script using HIGH_VLAUES in CDB_TAB_PARTITIONS and found the HIGH_VALUE column is missing in the CDB_TAB_PARTITIONS while the column is existing in DBA_TAB_PARTITIONS. Couldn’t find any reference in Oracle documentation (may be need a better search!) Why the column is missing in CDA view. Looking at the CDB_TAB_PARTITIONS view definition, oracle is using CONTAINERS clause to fetch all partition information, except the column HIGH_VALUE

SQL>; select TEXT from dba_views  (more...)

Changes – Personal and professional

Every organization needs to change for its survival and keep its competitiveness.  While change is not an easy procedure to complete, it can affect many lives both in positively and negatively.  The change owners may take intentionally or unintentionally wrong decisions   which can impact the stakeholders.  However, each individual should follow the same rules to come out of the change whether the individual it is affected positively or negatively.  Only the (more...)

LNS and LOG_BUFFER

In a oracle data guard environment Log Network Server (LNS) process transports the redo from the primary to the standby site. The behavior of LNS process is different from SYNC and ASYNC mode replication. In ASYNC mode transport, LNS read the redo from log buffer and hand over it to the RFS process in the target site. It is not necessary the redo is always available in the buffer cache. If there is not enough (more...)

Unified Auditing – some insights

Oracle 12c Unified Auditing is a brand new feature in the latest Oracle version which consolidates database level auditing records into a single location. DBAs can access the audit information from the view UNIFIED_AUDIT_TRAIL for all kind audit records, and they are

SQL> select distinct COMPONENT from all_unified_audit_actions;

COMPONENT
----------------------------------------------------------------
Direct path API
RMAN_AUDIT
Database Vault
XS
Label Security
Datapump
Standard
FineGrainedAudit

8 rows selected.

UNIFIED_AUDIT_TRAIL is a view owned by SYS and a public (more...)

PARTIAL Indexes

Oracle PARTIAL INDEXES – a new feature in Oracle 12c, initial impression was really good, but the implementation is quite poor. With this feature, you can define INDEXING OFF for a partition so that any index with PARTIAL clause will skip this partition while creating the index. The advantage is you can selectively create indexes on partitions. And for a global index or a global partitioned index, the rows from the INDEXING OFF partitions will (more...)

Tablespace growth history

Recently we had a tablespace space run out and ended up in an application failure.  I have questioned my DBA and he just plainly blamed the application team members who loaded large number records without a prior notice.  A convincing answer, but you can’t really fool Oracle.

Oracle introduced a new DBA_TABLESPACE_USAGE_METRICS view from 10g onwards to report the space usage with in a tablespace.  I created a new tablespace and immediately (more...)

x$bh and consistency

Oracle caches the data blocks in buffer cache in various modes depends on the block usage.  As per the Oracle documentation it can CR (Consistent mode – reads), XCUR (Current mode – updates), FREE etc.   I understand and other heard saying – whenever a block READs into memory will be in CR mode while if the block is fetching for UPDATE it will be in XCUR mode so that sessions can apply the (more...)

Bind peeking and session cached cursor

Bind peeking is a nice feature in Oracle to have many optimized plans for an SQL for various bind values.  DBAs believe that bind peeking happens during a soft parse which will identify an alternate plan. Why do I say that?

 

Hard Parse: Parsing first time, nothing exists to bind peek

 

Soft Parse :  SQL cursor is existing and executing not the first time.  Under the soft parse, bind peeking (more...)

CRS Timezone

Interesting problem – database was running normally without any issues and added to OCR.  But the log file started reporting a different time for all activities – for example.

Database and server is showing a time 4:25 while alertlog is ahead of 5 hours @9:25!

<pre>
oracle@prod # tail alert_xxxxxxx.log

Recovery of Online Redo Log: Thread 2 Group 16 Seq 129057 Reading mem 0

  Mem# 0: +ORAINDEX1/prod/onlinelog/group_16.282.864560747

Mon Jan 12  (more...)

enq: SQ – contention

Yesterday, I have seen huge waits “enq SQ – contention’”  – in every snapshot there were thousands of waits.  But the fix was so simple!  Here is the root cause of the issue –

When you select from a sequence, the NEXTVAL generated from a the seq$ table if it is not cached.  If it is cached, it will be available in a memory structure and no need to generate the value (more...)