Oracle http://cs.scu.edu.cn/~zuojie/oracle/server.101/b10755/waitevents004.htm - list with parameter values https://students.kiv.zcu.cz/doc/oracle/server.102/b14211/instance_tune.htm - with explanation Oracle Wait Interface - the whole book online buffer busy wait - two users trying to modify the same block at the same time buffer exterminate - SGA cache is shrinking - add more memory to SGA data file init write - datafile size is being increased db file parallel read - parallel read from multiple data files at same time db file scattered read - multi blick read usuaull a full table scan or fast full index scan db file sequential read - single block read usually index access or rowid acces, undo is also accessed this way direct path read - reading into private memory outside of buffer cache, used by PQO direct path read temp - reading data written to temp , usually a sort direct path write - direct path writes, like loader, writing above the high water mark direct path write temp - writing data to temporary tablespace, usually sorts enq: CI - Cross Instance- indicative of high incremental checkpointing and waiting on blocks being checkpinted - increase fast_start_mttr_target enq: HW - High Water- contention on moving up the high water mark - move object to ASSM or add freelists enq: KO - fast object checkpoint- used by PQO to clear changes from buffer cache, reduce fast_start_mttr_target enq: RO - reusable object- clearing cache for object drop/reuse, use gtt if possible, tune DBWR enq: TM - table modification- table (object) lock, often caused by foreign keys lacking index enq: TX - Transaction locks- application issue, more than one users chaning same data enq: UL - user lock- custom application locks. Look into application logic. free buffer wait - waiting for a free buffer in buffer cache to read data of disk into kksfbc child completion - related to high parsing, running 'insert into t value(1)' in a tight loop produces this (note error "value" instead of values) latch: library cache- usually indicates too much hard parsing latch: shared pool latch - latch used when allocating memory in shared pool, inidcative of too much hard parsing latch: cache buffers chains - over active datablock access - check SQL involved latch: cache buffers handles - increase _db_handles_cached latch: cache buffers lru chain- contention on the data block cache library cache load lock - multiple users waiting for same SQL to be compiled library cache lock - user trying to compile code and can't access it in exclusive access library cache pin- user trying to compile code and can't access it in exclusive access local write wait - usually from truncating and waiting to clear out buffer cache log buffer space- log buffer too small or log device too slow log file switch (archiving needed)- all DML hangs, archiver is stuck, usually because of full disk. Make space log file switch (checkpoint incomplete) - log files too small log file switch (private strand flush incomplete) - log files too small log file switch completion - log files too small log file sync - too many commits and/or log device is slow read by other session- multiple users waiting for IO read off of disk row lache lock- if on Sequence cache, then find the sequence and increase number cached SQL*Net break/reset to client - error in SQL statement SQL*Net break/reset to dblink - error in SQL over DB link SQL*Net message to client - time to pack a message (no network time included) possibly tune SDU SQL*Net more data from client - possible network issues, possibly tune SDU SQL*Net more data from dblink- possible network issues, possibly tune SDU SQL*Net more data to client- time to pack a message (no network time included) possibly tune SDU write complete wait - waiting for DBWR to finish writing a dirty block to disk , increase cache size or speed up DBWR SQL Server Sybase DB2 |