Technical data

Poor autorefresh performance
Troubleshooting Oracle In-Memory Database Cache 4-27
Number of updates that has not been marked with a valid logseq: 0
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Host name: conobar-tt
Timesten datastore name: /scratch/ds/myDB
Cache table name: SCOTT.A
Change log table name: tt_05_1279699_L
Number of rows in change log table: 7
Maximum logseq on the change log table: 0
Timesten has autorefreshed updates upto logseq: 0
Number of updates waiting to be autorefreshed: 5
Number of updates that has not been marked with a valid logseq: 5
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2. Manually alter the table on the Oracle database. The following example uses the
table from the previous example. This example alters the INITRANS and
FREELISTS settings for the bar.tt_05_1279699_L table.
ALTER TABLE BAR.TT_05_1279699_L INITRANS 10;
ALTER TABLE BAR.TT_05_1279699_L STORAGE(FREELISTS 5);
or
ALTER TABLE BAR.TT_05_1279699_L MOVE STORAGE(FREELISTS 5);
3. Alter the INITRANS and FREELISTS settings for the index for this table, which
have the same name as the autorefresh change log table with an additional "L" at
the end of it. For example, the index for table bar.tt_05_1279699_L is
bar.tt_05_1279699_LL
These settings should be the same as what you set for the autorefresh change log
table.
ALTER INDEX BAR.TT_05_1279699_LL INITRANS 10;
ALTER INDEX BAR.TT_05_1279699_LL STORAGE(FREELISTS 5);
Abnormally large log and base tables degrade autorefresh performance
The cache thread SQL refresh joins the log table and the base table, which identifies
rows needed to be refreshed into TimesTen. The larger the cardinalities of the base
table and the log table, the longer the time necessary to perform this join. Performance
degradation may occur if either the log table or the base table is abnormally large.
The following describe scenarios where the log table can become abnormally large:
■ If the log table is never purged in configurations where cache groups from
multiple DSNs all reference the same base table, it increases in size indefinitely. If
one or more of the cache agents for these groups are turned off, those DSNs will
not properly refresh their cache groups and the log tables will not be purged. If the
autorefresh state is turned to paused on one of multiple nodes, the other nodes
may slow down.
■ The log table can grow abnormally large if some of the cache agents have been
shutdown. Resolve this issue by restarting the cache, which will purge all of the
backlogged log rows to be purged and all of the cache groups to be synchronized
after the completion of the refresh cycle for all cache groups.
Note: See "INITRANS integer" and "FREELISTS" in the Oracle
Database SQL Language Reference for details on what are the correct
values for configuring these settings.