doc-exports/docs/dws/dev/dws_04_0898.html

<a name="EN-US_TOPIC_0000001811490785"></a><a name="EN-US_TOPIC_0000001811490785"></a>

<h1 class="topictitle1">Asynchronous I/O Operations</h1>
<div id="body8662426"><div class="section" id="EN-US_TOPIC_0000001811490785__sf18d1368b44a45a68de6ca9e975a8e77"><h4 class="sectiontitle">enable_adio_debug</h4><p id="EN-US_TOPIC_0000001811490785__a3eefaf0871fd4849a83a969cfc67ca5a"><strong id="EN-US_TOPIC_0000001811490785__b1436105634513">Parameter description</strong>: Specifies whether to enable logging related to ADIO, which helps to locate ADIO-related issues. General users are not advised to set this O&amp;M parameter.</p>
<p id="EN-US_TOPIC_0000001811490785__p18312194119317"><strong id="EN-US_TOPIC_0000001811490785__b1783416012234">Type</strong>: SUSET</p>
<p id="EN-US_TOPIC_0000001811490785__a8d2cc5c6adb84537ac3da571b7aa9c6c"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778487_aa1fc9bedad6b4779a216c176c5046dcc">Value range</strong>: Boolean</p>
<ul id="EN-US_TOPIC_0000001811490785__u1903e405a11149ce9fa8addc3c06b3be"><li id="EN-US_TOPIC_0000001811490785__l622550f5ea85463e8b0b0ee7e0469273"><strong id="EN-US_TOPIC_0000001811490785__b842352706102618">on</strong> or <strong id="EN-US_TOPIC_0000001811490785__b84235270611225">true</strong> indicates the log switch is enabled.</li><li id="EN-US_TOPIC_0000001811490785__l0864563c41a6474da2c46a77f640f152"><strong id="EN-US_TOPIC_0000001811490785__b842352706102625">off</strong> or <strong id="EN-US_TOPIC_0000001811490785__b842352706112227">false</strong> indicates the log switch is disabled.</li></ul>
<p id="EN-US_TOPIC_0000001811490785__a3178b4dcd92b4db992cf310264fb2c7d"><strong id="EN-US_TOPIC_0000001811490785__b14485191810400">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b24877187409">off</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__s9ecf8b98172d4255a3affe4970e11f39"><h4 class="sectiontitle">enable_fast_allocate</h4><p id="EN-US_TOPIC_0000001811490785__a7f4fab7a86b148d9aef376c002c682a8"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_a67cf89f508664cba9af034968fe95953">Parameter description</strong>: Specifies whether the quick allocation switch of the disk space is enabled. This switch can be enabled only in the XFS file system.</p>
<p id="EN-US_TOPIC_0000001811490785__p1530123020336"><strong id="EN-US_TOPIC_0000001811490785__b944016314234">Type</strong>: SUSET</p>
<p id="EN-US_TOPIC_0000001811490785__a7bb8d838cdf54e1c9181ca343cfa7ee6"><strong id="EN-US_TOPIC_0000001811490785__b1641531698">Value range</strong>: Boolean</p>
<ul id="EN-US_TOPIC_0000001811490785__ucc08d334b1724739a3bfd51dc6a7e09f"><li id="EN-US_TOPIC_0000001811490785__l817d5431dcb04db4b9e7338e132c0184"><strong id="EN-US_TOPIC_0000001811490785__b2039919125">on</strong> or <strong id="EN-US_TOPIC_0000001811490785__b141632335">true</strong> indicates that this function is enabled.</li><li id="EN-US_TOPIC_0000001811490785__l4cfd6d2de4ca404398155d4eb2ba7012"><strong id="EN-US_TOPIC_0000001811490785__b1969569797">off</strong> or <strong id="EN-US_TOPIC_0000001811490785__b151152839">false</strong> indicates that the function is disabled.</li></ul>
<p id="EN-US_TOPIC_0000001811490785__aee252c6cdd8c443ca3170b51dffe5fe1"><strong id="EN-US_TOPIC_0000001811490785__b2948181912401">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b69504197405">off</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__s385ba4b4603140c8865930209a62c6a3"><h4 class="sectiontitle">prefetch_quantity</h4><p id="EN-US_TOPIC_0000001811490785__a3137eebb37404e9a93bf1248947bffd4"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_en-us_topic_0058967784_b25941690">Parameter description</strong>: Specifies the number of row-store prefetches using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p128281733143419"><strong id="EN-US_TOPIC_0000001811490785__b312917612310">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__aa8bf52050e2048fea295b855430d5ea7"><strong id="EN-US_TOPIC_0000001811490785__b29791968172314">Value range</strong>: an integer ranging from 1024 to 1048576. The unit is 8 KB.</p>
<p id="EN-US_TOPIC_0000001811490785__a14b53d78e1d3404e9b2a0383a9f1eec5"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0058967784_b4034845193810_1">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b842352706112720">32 MB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__sbc8ec9ebcfc640e2a24ff43fc1ff4be7"><h4 class="sectiontitle">backwrite_quantity</h4><p id="EN-US_TOPIC_0000001811490785__a4dd1e597e8684e7ca3387b3e3a71cb71"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_aa98c8bbf28c448d78d2b47b1fd570b5a">Parameter description</strong>: Specifies the number of row-store writes using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p148301157353"><strong id="EN-US_TOPIC_0000001811490785__b125886611238">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__a8e81cc6071ae46c4b165bf1deef05441"><strong id="EN-US_TOPIC_0000001811490785__b54663584615">Value range</strong>: an integer ranging from 1024 to 1048576. The unit is 8 KB.</p>
<p id="EN-US_TOPIC_0000001811490785__a398a5ad4ec764503b1dc1f1d314a09cd"><strong id="EN-US_TOPIC_0000001811490785__b5735075_1">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b842352706103633">8MB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__s5c15fa7d33a7478587eb5f1a2c3f2e21"><h4 class="sectiontitle">cstore_prefetch_quantity</h4><p id="EN-US_TOPIC_0000001811490785__a21c2b1bdeaf249f8a2be884d5491735b"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_a48280c27c53a4ec295287d3f3dbc767d">Parameter description</strong>: Specifies the number of column-store prefetches using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p88871315143515"><strong id="EN-US_TOPIC_0000001811490785__b133345752317">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__a6373ef9464884807b18fccb0b7eaf7a0"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0085033176_en-us_topic_0059778686_a8791c882938f4e6c9ae407641e405449">Value range</strong>: an integer. The value range is from 1024 to 1048576 and the unit is KB.</p>
<p id="EN-US_TOPIC_0000001811490785__a3f3557b6481c4a67a263967a0f3a4602"><strong id="EN-US_TOPIC_0000001811490785__b2035932827">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b1482072288">32 MB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__sa690f9f51849458e982e1a6ca69363c0"><h4 class="sectiontitle">cstore_backwrite_quantity</h4><p id="EN-US_TOPIC_0000001811490785__acc6e3528a50c4a8ba2635f243d4eaec2"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_af13e9353c4b74526b9074a68685f3522">Parameter description</strong>: Specifies the number of column-store writes using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p118301124163513"><strong id="EN-US_TOPIC_0000001811490785__b7797147112316">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__a6451f48b5b86414991a3be333ef389f8"><strong id="EN-US_TOPIC_0000001811490785__b2026312335">Value range</strong>: an integer. The value range is from 1024 to 1048576 and the unit is KB.</p>
<p id="EN-US_TOPIC_0000001811490785__a975801a4554442e4b3a429659c793f9a"><strong id="EN-US_TOPIC_0000001811490785__b1384937530">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b1242604383">8MB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__seaab60884f1c414aac0196dfdb4cb0c6"><h4 class="sectiontitle">cstore_backwrite_max_threshold</h4><p id="EN-US_TOPIC_0000001811490785__a487d757da470400ea5de3cf6c8397eea"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_a9ba629bc662648429ce76d1cb6fa9123">Parameter description</strong>: Specifies the maximum number of column-store writes buffered in the database using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p14479935143513"><strong id="EN-US_TOPIC_0000001811490785__b5158813231">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__a989d8c501ed44edea2d2a688b9eecf3a"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0085033176_en-us_topic_0059778686_a12aff2b535754af2851176a2e69ea575">Value range</strong>: an integer ranging from 4096 to INT_MAX/2, in KB</p>
<p id="EN-US_TOPIC_0000001811490785__a2f1f5eb35f1746bfaf47647c5cc73379"><strong id="EN-US_TOPIC_0000001811490785__b573446154754">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b84235270617188">2 GB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__s049e3eefe5b74beb8961d1e4d0326faa"><h4 class="sectiontitle">fast_extend_file_size</h4><p id="EN-US_TOPIC_0000001811490785__afbe602f900f7466cb0ca05afd855a642"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_aacfa07a1399f49838e7aa89be9732d1b">Parameter description</strong>: Specifies the disk size that the row-store pre-scales using the ADIO.</p>
<p id="EN-US_TOPIC_0000001811490785__p19440346153516"><strong id="EN-US_TOPIC_0000001811490785__b11199128132310">Type</strong>: SUSET</p>
<p id="EN-US_TOPIC_0000001811490785__aff6cae05dfe14535804cc63bd4f48f03"><strong id="EN-US_TOPIC_0000001811490785__b812364116">Value range</strong>: an integer. The value range is from 1024 to 1048576 and the unit is KB.</p>
<p id="EN-US_TOPIC_0000001811490785__a5b5978c2ead44ffb80d1eba6edb4131f"><strong id="EN-US_TOPIC_0000001811490785__b133856019">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b1258383547">8MB</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__sb1e39f7916124015a9460f0c46dd9ab5"><h4 class="sectiontitle">effective_io_concurrency</h4><p id="EN-US_TOPIC_0000001811490785__a6f9c59ea3f094f1c885c8fa4753d53b3"><strong id="EN-US_TOPIC_0000001811490785__en-us_topic_0059778686_b57302975171119">Parameter description</strong>: Specifies the number of requests that can be simultaneously processed by the disk subsystem. For the RAID array, the parameter value must be the number of disk drive spindles in the array.</p>
<p id="EN-US_TOPIC_0000001811490785__p18215142243619"><strong id="EN-US_TOPIC_0000001811490785__b4407186239">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__a98e50d2bf7c047bda60ddd93648b04a8"><strong id="EN-US_TOPIC_0000001811490785__b17371103215282">Value range</strong>: an integer ranging from 0 to 1000</p>
<p id="EN-US_TOPIC_0000001811490785__a76461f6ed1514058ae84275849c3991f"><strong id="EN-US_TOPIC_0000001811490785__b3158552610564">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b842352706173228">1</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__section7995832812"><h4 class="sectiontitle">cu_preload_max_distance</h4><p id="EN-US_TOPIC_0000001811490785__p20811121915584"><strong id="EN-US_TOPIC_0000001811490785__b96071431817">Parameter description</strong>: Specifies the maximum number of CU groups that can be prefetched. This is supported only by clusters of version 9.1.0.100 or later.</p>
<p id="EN-US_TOPIC_0000001811490785__p5680142514588"><strong id="EN-US_TOPIC_0000001811490785__b819721976">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__p423372945814"><strong id="EN-US_TOPIC_0000001811490785__b193071420637">Value range</strong>: an integer ranging from 0 to 1024. The value <strong id="EN-US_TOPIC_0000001811490785__b1653117251138">0</strong> indicates that prefetching is disabled.</p>
<p id="EN-US_TOPIC_0000001811490785__p143789139585"><strong id="EN-US_TOPIC_0000001811490785__b8789192425415">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b4789024205411">20</strong></p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811490785__section4780104634718"><h4 class="sectiontitle">cu_preload_count</h4><p id="EN-US_TOPIC_0000001811490785__p202013386472"><strong id="EN-US_TOPIC_0000001811490785__b0638143914319">Parameter description</strong>: Specifies the maximum number of CUs to be prefetched. This parameter is supported only by clusters of version 9.1.0 or later.</p>
<p id="EN-US_TOPIC_0000001811490785__p1420173844719"><strong id="EN-US_TOPIC_0000001811490785__b366889202">Type</strong>: USERSET</p>
<p id="EN-US_TOPIC_0000001811490785__p353015820472"><strong id="EN-US_TOPIC_0000001811490785__b64781519202720">Value range</strong>: an integer. The value ranges from 0 to 10000. The value <strong id="EN-US_TOPIC_0000001811490785__b9314758631">0</strong> indicates that prefetching is disabled.</p>
<p id="EN-US_TOPIC_0000001811490785__p7163175344716"><strong id="EN-US_TOPIC_0000001811490785__b11977192943819">Default value</strong>: <strong id="EN-US_TOPIC_0000001811490785__b9977152919389">600</strong></p>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0892.html">Resource Consumption</a></div>
</div>
</div>