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Hello All, IAOUG is back again in Australia for its second year consecutive year OTN Days, with Arup/Tim Hall/Connor around, two conferences being planned, please checkout if you are around Sydney / Goldcoast / or in Australia. http://www.iaoug.com/home.html Sydney, October 31st 2016 At […] Find the best way to find how much time the query (sql_id) has ran in past or current ASH stores whenever a session is active every second in v$active_session_history for past two hours, In rotation one sample of every 10 seconds will be visible to dba_hist_active_session_history. From v$active_session_history select to_char(sample_time,’DD-MON-YY HH24′) Time, sql_id,sql_plan_hash_value,sql_exec_id,round((count(*))/60/60, 2) […] As like in ASM, when ever a disk is added a rebalance operation takes place between the disks, similarly when the replication factor is changed at keyspace level in the cassandra, the rebalance operation should take place, I have changed the replication factor for Keyspace and you should start the repair of each node so […] Undo like pointers, tombstones Cassandra uses a log-structured storage engine. Because of this, deletes do not remove the rows and columns immediately and in-place. Instead, Cassandra writes a special marker, called a tombstone, indicating that a row, column, or range of columns was deleted. These tombstones are kept for at least the period of time […] Backup in Cassandra maintain at node level , so any backup that taken in the one node does not contain other nodes data, so you must take backup of each node, cassandra maintains backups as snapshots means an entire sstables at disk level copied to a different folder with snapshot id as like below. root@wash-i-16ca26c8-prod […] As like oracle 100046 , you can also trace the Cassandra Session and it provide you the following information , the highlighted blue parts are important to understand that data has been fetched from different nodes and how many undo it has to read and how many from cache and how many reads […] Shutdown Best Practice While Cassandra is crash-safe, you can make a cleanershutdown and save some time during startup thus: – Make other nodes think this one is down. – nodetool -h $(hostname) -p 8080 disablegossip – Wait a few secs, cut off anyone from writing to this node. – nodetool -h $(hostname) -p […] Partition Merging or Compact or merging ss tables Cassandra does not do in-place writes or updates. Rather, it uses a log structured format. Writes are done to Memtables, which are periodically flushed to disk as SSTables. As a result of this approach, the number of SSTables grows over time. Having multiple SSTables causes […] |
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Oracle 23c New Features for DBA's
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