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Jonathan Lewis on 24 January 2017 with 0 comments

While looking at the results from a query against the dynamic performance view v$active_session_history during a recent trouble-shooting assignment I noticed a result that was so unusual that I decided I needed to get some information from the v$ash_info view over an interval of about 3 minutes – and it didn’t matter which three minutes in particular, any three (consecutive)… Continue Reading →

12c, All Things Oracle Full Articles, Oracle Database, Troubleshooting

In my book “Cost Based Oracle – Fundamentals” (Apress 2005) I described a problem with the cost calculation for the index fast full scan: When you generate statistics for a table, one of the results is the number of blocks below the high water mark. When you generate the statistics for an index, you get the number of leaf blocks… Continue Reading →

10g, 11g, 12c, All Things Oracle Full Articles, Oracle Database, Troubleshooting

In Oracle Database 12c, you can set a column in table as invisible either during CREATE TABLE or modifying existing table via ALTER TABLE command. By default, table columns are always visible. When you make it invisible, the COL# column in COL$ dictionary is updated to 0, and so is not included in the “SELECT *” or “INSERT INTO VALUES”… Continue Reading →

12c, All Things Oracle Full Articles

Introduction Oracle Database 10g Release 1 introduced Automatic Storage Management (ASM), a new framework for managing Oracle database files. ASM provides a foundation for highly efficient storage management with direct I/O, redundancy, striping and load balancing. Files stored on ASM are evenly distributed across disks in a disk group and mirrored according to the policies defined in the disk group…. Continue Reading →

10g, 11g, 12c, All Things Oracle Full Articles

The Oracle Database In-Memory option was introduced in Oracle 12c (12.1.0.2 patch set). By using the In-Memory option, businesses can benefit from better decisions made in real time, improved productivity, increased competitiveness and lowered costs. The Oracle In-Memory option is designed to fit both Data warehouse and mixed workload OLTP databases, and can be deployed with any existing application that… Continue Reading →

12c, All Things Oracle Full Articles

Cloning of a Pluggable Database (PDB) in Oracle Multitenant is a great feature and is very useful. Oracle Database 12c Release 1 has introduced various enhancements to the cloning of Pluggable Databases to overcome the limitations imposed by the initial release of Oracle Database 12c (12.1.0.1). In Oracle 12.1.0.2c: PDBs can be hot cloned, i.e. you don’t need to put the source PDB… Continue Reading →

12c, All Things Oracle Full Articles

In the initial release of Oracle 12c (12.1.0.1c), a non-Container Database (non-CDB) could be converted to a pluggable database (PDB) using any of the following methods: Using DBMS_PDB Using datapump (expdb, impdp) Using GoldenGate replication The 12.1.0.2 patchset has introduced the ability to clone a remote non-CDB as a PDB directly over the network. Remote Cloning of a Non-CDB is a… Continue Reading →

12c, All Things Oracle Full Articles

In the previous installment of this series I produced some figures highlighting the main differences between doing a large delete by tablescan and doing a large delete by index range scan. Depending on the data patterns involved the correct choice of strategy could make a significant difference to the number of random I/Os, the volume of redo generated, and the… Continue Reading →

12c, All Things Oracle Full Articles

Oracle 12c has introduced Flex Clusters which use hub-and-spoke technology, allowing the cluster to scale much beyond the pre-12c clusters as it requires: Fewer network interactions between nodes in the cluster, and : Less contention for key Clusterware resources like OCR and voting disks. A Flex Cluster has two types of nodes: Hub Nodes and Leaf Nodes. Hub Nodes These… Continue Reading →

12c, All Things Oracle Full Articles

In an earlier article, I discussed Automatic big table cache (ABTC) which is a new feature introduced in Oracle Database 12.1.0.2c. Automatic big table cache is an optional section of the buffer cache reserved for storing large objects. It tracks only big tables and automatically caches scanned big objects in big table cache thereby avoiding direct path reads. It caches… Continue Reading →

12c, All Things Oracle Full Articles